Yes, I hate that!
I do, however, have a half slip that I bought to wear with my itchy wool skirt. I wear it maybe twice a year.
teela, as far as pantyhose go, I’m trying to wean myself away from them since they’re apparently Just Not Done anymore. I’m barelegged today as a matter of fact. I can’t see as how I’ve done the world any favors with the display of my bruised white skin, though. I completely gave up the nude pantyhose, but I still have some off-black pairs and a couple of fishnets.
I wear half-slips with clingy or sheer skirts. The sheer skirts aren’t made of gauze, but some really lightweight fabrics are a bit sheer, especially if you are standing somewhere with a lot of bright light behind you.
Note: This is Florida. You want the lightest weight fabrics you can find. If that means it’s a “cheap piece of crap” then so be it. You sweat your butt off then. My shit likes to breathe. That said, wearing a synthetic fabric skip with a nice linen or cotton dress or skirt pretty much defeats the purpose of “light, cool, and comfortable.” I’ve tried and tried to find cotton slips, but they are very difficult to find. I got one from The Vermont Country Store, but it was like a long baby t-shirt and not very attractive. And a rather heavy weight cotton for Florida (Nice when the temps cool… for two months out of the year, otherwise, not really worth the shipping).
Anyway, if anyone can point me to natural fiber slips, you’ll be my fashion hero for the week.
Oh, and P.S. I don’t wear pantyhose unless I’m going to be in an important meeting or a job interview with Big Wigs and have to wear a suit and look all spiffy and professional. The rest of the time, I look as professional as is possible without pantyhose. It’s just too dang hot down here for those things.
If you wear the right slip, it can do double duty on a date. 
But to the OP’s point, I think that slips are considered old ladyish, but I also think that’s unfortunate because they can minimize pantyline if you don’t want to wear a thong or want to make an otherwise questionable (almost sheer) dress more appropriate.
They’re hard to find these days - I have a few for skirts that are sticking to my legs.
I wear slips and half-slips under sheer dresses/skirts. During hot weather, I wear pettipants under some sundresses to prevent chafing, although they look comically grannyish! In situations where I cannot go bare-legged under a dress, I no longer wear hose from an egg, but instead wear thigh high stockings, which are sexier and less bulky.
Half slips when appropriate, as many others have already mentioned. For the reason that you might wear a certain type of bra under a certain type of shirt, or a cami under a blouse, or whatever. For people to consider them old-fashioned and obsolete is just crazy talk. You may never wear a skirt/dress that requires one, but I would also bet that sometimes one is really required and you don’t realize it. It’s like that famous picture of Diana Spencer that was taken at the kindergarten where she worked after the announcement of her engagement to Charles. With the way the light was behind her and with the lasting image of the photo, the skirt became almost see-through.
I wore a slip just the other day, to the family reunion. The knee length skirt I have I absolutely love and is not sheer, but it tends to be floaty and when a breeze picks up… up it goes. So to prevent showing my underwear off to all my relatives by accident (75% of the people there were my Grandparents age) I wore a slip.
I didn’t find it uncomfortable in the slightest, and it was one of the hottest days this summer. And I was really glad I wore it because when we returned Great-Grandma to the nursing home the wind DID pick up and lift my skirt.
If the skirt needs it, then yes I’ll wear one. I also wear cami’s regularly, as underclothes. That’s mainly because I have a nickel allergy and even though my belt is claimed to be nickel free I get a rash sometimes if I don’t wear something between my skin and it so it tucks in. Which does double duty because being tall as I am, most shirts (especially dress shirts) tend to be too short and rise up which doesn’t look so great at work.
Pantyhose though? That’s the spawn of the devil and the worst invention ever.
I’m only 35, but I’m apparently very old fashioned. I prefer to wear slips with dresses and skirts. It’s hot here, and the sticking problem is legion. With a slip, the slip sticks, the skirt hangs properly. It also cuts down on the sweat-staining and deodorant-staining, which cuts down on the dry cleaning bills. I’m also fond of stockings and garters, especially if I haven’t shaved in 2 days. I actually have a very silky pants-liner to wear under dress slacks, as well, to prevent the sticking/hanging wrong problem. I don’t wear those as often, but I do wear them.
I have a black full slip, and I feel like a movie star in it. I don’t want to put anything over it! And regular skirt slips, too. But do I wear them? Not very regularly, and even when I probably should. I’ll be re-thinking them now, though. I just tend to wear a skirt or dress that might be see-through on cloudy summer days instead of bright ones. 
Yes, apparently pantyhose are no longer necessary, and I haven’t worn them except to a job interview (I got the job…) but I don’t wear short skirts, so not a whole lot of my pasty-white, plump, and scarred legs show. For winter, I do wear black hose a lot. That’s when the pale white legs, with accessory scars, seem to really stick out, and I do think black hose looks much more polished.
I’ve been thinking of just making a couple of half-slips out of unbleached muslin or something similar. It can’t be that hard. I think that nylon slips are the work of the Devil, who hates women even more than Paul did. However, enough fabric softener will help prevent the slips from clinging so badly.
Try some women’s boxers, or boxer briefs. They prevent chafing, and are actually cooler, in my experience, than briefs. I am not going to comment on hose, as they are another invention of the Devil.
I wear half slips anytime I wear a skirt or a dress. It keeps the dress from bunching up and can help with static cling. It also helps when it’s hot and sweaty outside…I can tuck the slip between my legs if I need to to prevent chafing (currently out of pettipants) which is a much better solution than tucking the skirt between my legs!
I wear dresses or skirts almost every day (I just like them) and always wear a trouser like half slip aka pettipants. They rock. Even if they do show when I’m on my bike.
I also sleep in them in the summer.
I have one skirt and one dress that require slips. The skirt is clingy so without a slip it looks ridiculous. The dress is a knit Missoni type thing so a nude slip underneath is essential, plus it makes the dress lie more smoothly.
Of course I wear a slip, if I need one, at least a half-slip. I once needed a pink one for a transparent pink skirt - found a pink one in the thrift store, washed well, voila. (I only wore the skirt twice, didn’t want to spend $15 and all day shopping for a new pink slip.)
My wife wears them fairly often. She’s not terribly young, but not old (near 40).
I thought of that whe I first saw this thread too. There was worry that the photo might derail the engagement. I’m sure it was her worst fear at the time, but think how much happier she might have been!
Pantyhose - I’ll never give them up. My extremely white Irish skin needs to be filtered or people could be blinded in the sunlight. I’ll be an old lady sitting on the porch whining to my grandchildrent hat I have to send away to third world countries to buy them anymore. . . Plus your shoes get all yucky if you wear them without some sort of stocking.
I’m relieved that I’m not the only person left under 70 who still wears a slip, or at least a half-slip. I agree that it’s inconvenient in the summer, but generally, I’m more worried about the cling factor and the see-through factor, since it doesn’t get all that hot here for very long. As for panty hose, I don’t wear 'em, but I do wear tights, and I have quite a collection. If I’m wearing high boots, I wear lycra footless tights and actual socks. It’s all about the comfort, and I’m not in a very formal setting.
Wow. I wouldn’t even know where to look to buy a slip. Then again, I wear a skirt or dress maybe 3-4x/year, and both of my skirts are denim.
I have one skirt that I have to wear a half-slip with. It’s white cotton, and even though it is lined, you can still see through it on a sunny day.
I’m 24, and it didn’t even occur to me that it would be old-fashioned to wear a slip.
Not anymore, not since the mandatory church attendance of my misspent youth.
What matters is not how you wear a slip, but how you slip out of what you wear.
I tentatively believe I’ve coined a new bon mot there… the first four pages on Google turned up nuthin’.