In England, “dressing up” and “fancy dress” both mean wearing a costume, rather than formal dress. Always makes me wonder how many Brits show up at snooty cocktail parties in the USA dressed as Spongebob.
Personally, I enjoy wearing costume, sometimes, especially if I can make the costume myself. I have a few sort of acceptable formali-ish dresses around, but I very rarely wear them.
I like wearing costumes. I’ve made some great ones in the past - like my husband’s shark outfit or the Energizer Bunny costume, or my black widow spider outfit…
But lace and sequins and shoes that kill my feet just don’t appeal.
One of the great things about being Donald E. Westlake’s editor for 15 years is the endless collection of anecdotes about the funny-ass shit he said.
I was taking a half-dozen well-known mystery authors to dinner at a fancy dee loox restaurant in DC, and we were all dressed appropriately for the occasion. Cocktails were ordered, menus were awaited, Don looks around the table and says “Okay. We’ve all seen each other’s neckties by now, right?” Proceeds to yank his off and toss it under his chair.
Other males at the table smile broadly and do the same.
“Where are all the other tarts and vicars?”
Are you me??? 
Nah, I hate lobster, my husband has never owned a leisure suit, and we’ve never been on a cruise.
I rarely dress up. I have very few dressy things - had to buy new clothes for niece’s wedding 2 years ago. I work from home these days so I don’t even have much “business casual” clothing. I live in jeans, T-shirts, and a few non-T-shirt tops. I’d probably avoid a cruise that had a Formal Night (unless they all do?) just because I wouldn’t want to bother.
I’ve never been dressed up more than a business suit, and when I do don it once every couple years, I am impressed by the result, for like a half an hour but then it gets hot and uncomfortable and beforehand I’m always worried if the suit will still fit.
On the other hand, when the weather is cold I do wear a long overcoat over just regular clothes because it looks better than an outdoorsy winter jacket. Plus it’s big enough that if it’s really cold I can wear a winter jacket under it for even more central body warmth.
Hell to the no!
Its hard to find something that fits (tall, long, broad shoulders) and that I feel comfortable in.
I ONLY like dressing up if the Mrs does as well and wears sexy undergarments and knowing a night of lust is before me.
Not even a little bit. Mostly because it requires shopping. I have one funeral outfit and the rest of my attire is 100% cotton tees and yoga pants/shorts. I don’t wear makeup and my hair is braided most of the time. Getting dressed up for me is putting on a bra and wearing my hair down. If it’s really special I’ll wear one of my non-stained shirts. 
Absolutely love putting on the monkey suit. I would be a dandy, if I had the resources; one of my if-I-won-the-lottery fantasies is walking into a Savile Row bespoke tailor and ordering four suits (solid navy, chalk pinstripe navy, solid gray and pinstripe gray, of course). As well as the shirts, ties, shoes and such to go with them.
I haven’t had too many occasions to wear a tuxedo - a wedding and a prom, basically - but I felt I looked fantastic, and thoroughly enjoyed the experience. Same thing for wearing Scottish formal dress. (Pace notquitekarpov, I would never wear a kilt in Great Britain - feel a little hesitant about even a tartan tie or scarf - since I’m not Scottish. But I am Scottish-American, and in the US, that’s what wearing a kilt signifies.)
ETA: Also, what Shodan said in Post #71.
As a man I’ve always felt it was inconsequential.
If you can button your collar, then wearing a tie is not a problem
If you can wear a tie, then you can wear a suit
If you can wear a suit you can wear a tuxedo
If you can wear a tuxedo your can wear morning or evening dress (okay, you also need a vest)
So, start with a shirt you can button comfortably and the rest falls into place. Of course, it also means wearing dress shoes, but I’m good with that.
And yes, I look good in a suit. And a tux. And a morning coat.
My attire is khakis and black dressy tee shirt, with Birkenstocks or Danskos. I did go on one cruise once and for the dressy day, I sported fancy sandals. From Payless. 
On the rare occasion where I do have to dress up, I not only loathe it during the event, but I loathe it during the weeks/months leading up to it.
“Fuck, I’m gonna have to wear a tie in 6 weeks”
I generate a mental countdown that, I’m convinced, is filled with the same level of dread as one awaiting his own felony criminal trial to commence.
mmm
This is important. I’m actually short and broad, so a suit is NOT designed for me, so I’ve generally hated them. Recently, I got two made to measure suits (there are several reputable places to do this, and the cost is pretty reasonable) and sweet Jesus do they fit well. I look and feel good in a suit for the first time, and I wear them whenever I can.
What are people thinking about as situations when they “have to” dress up?
I always have neat, clean clothes on even if I’m wearing jeans and a t-shirt. But I decided a few years back that I’m never wearing a suit again. I threw mine out. I gave a garbage bag filled with ties to Goodwill.
So far I haven’t encountered a situation where I “have to” don a suit. Maybe if I were under indictment for murder one I’d go back on my decision. But I’ve had my fill of cruises and I can’t think of another “have to” dress up situation.
What would you do if you are invited to an event where the expectation was a suit (wedding, state dinner) – decline the invitation?
You should visit my brother in laws store, Jimmy Aus, they are, I believe, the only men’s wear store that specializes in short men.
Are you saying to attend weddings and/or funerals in clean jeans and t-shirt?
mmm
Why not? Here in Hawaii, “Aloha attire” is commonly requested in notices for funerals. You wear it at weddings too. Anyone in a suit is going to stick out like a sore thumb. It all depends on the local environment inhabited.
Hell yeah! I absolutely love getting dressed up, and I’d do so way more often if I could. (It’s not always practical, of course)
In fact, I usually wear make-up even if I’m just sitting around the house in my pjs.