This may be a dumb question but …
Do they provide more comfort than ‘regular’ pants or are they just for looks/to make the women look more attractive?
They are super comfy and more flattering/accepted than sweatpants.
And the leggings style are way easier to tuck into your boots than a pair of jeans.
Sweater, leggings/yoga pants, boots. Uniform between November and April.
No matter the reason: Thank you.
Having heard the reason: That makes a lot of sense.
I’m gonna guess the primary reasons women wear yoga pants in public are that people stare when they just wear underpants, and sometimes it’s chilly that way.
Seriously, are women’s fashion choices a problem or something?
and you need to make sure you’ve shaved/waxed your legs too, to be socially acceptable that way 
You may as well ask, “Why do men wear sweats or basketball shorts in public?” The answer will be the same…they’re super comfortable.
No but required.
Why do people wear pajama pants in public?
I see what you did there.
Because men don’t have the proper curves.
Trust me on this. I did an experiment.
Don’t get me wrong, I fully appreciate seeing a callipygous lady in yoga pants. I was just curious what the primary purpose was.
Cuz we look bad in basketball shorts.
I recently floated this as a wardrobe option and was outvoted.
The purpose is to wear pants that are very comfortable. It doesn’t go any deeper than that. 
Oh, unless you think women wear yoga pants to turn men on? I don’t know, maybe some do. I wear them in public because they’re the most comfortable pants I have, and some days, a person just doesn’t want to deal with constricting pants, you know?
Well, do women wear make up because it feels comfortable? No. They do it to be attractive. One wondered if that was the same reason they wear yoga pants.
It seems I got some (probably fat) feminists riled up with this thread.
I think the question should actually be, “Why do women feel it’s OK to wear yoga pants in public, whereas in the past they would not have as said pants are too revealing.”
I find it to be a pretty titillating and immodest look. It would be like a guy wearing Speedo-level-tight, well, tights. So that you can see the full package in 3D, not to mention the buttcheeks well-highlighted.
Sweat pants are typically not that tight.
Camel toe is in evidence more than the wearers would probably like to think.
I’m not the fashion police and won’t say that women ought not wear yoga pants and leggings in place of regular pants, but I do find it surprising that so many find it comfortable to do so.
Sigh. You give men a bad name.
All right. I opened this thread, and immediately thought, “Wow, yoga pants in public? That’s like sweatpants, right?” Maybe I don’t actually know what yoga pants are–although as I said, I’ve gone to a yoga class. People were wearing all kinds of things but the most prevalent seemed to be what looked like a short, lightweight pair of sweat pants that fell just below the knee. Some people were wearing shorts.
So I googled it. Wow. I have to say, I have never seen any woman in public the way those Google images are. So I think there is some confusion here.
If the thing they’re wearing is translucent because it’s stretched, it’s not yoga pants. It’s not even leggings. It’s tights, which should not be worn as pants. If you can see the contrasting color thong underneath, she is definitely wearing it to titillate.
If the thing they’re wearing is merely tight, they should probably be wearing a tunic or some other top that falls below their hips.
If it’s tight but has belt loops, it’s not yoga pants.
Yoga pants, as worn to actual yoga classes, are not all that revealing. In fact a lot of them are downright drapey, and some of them are quite loose-fitting. So this yoga pants thing is not actual yoga pants, but something else.
Also, any of the women in the last yoga class I went to could have decently worn the same outfit out shopping or wherever. Not one of them was in any way immodest.
My point here is that I would like to know what kind of “yoga pants” the OP is seeing, out and about. If it’s the kind found when googling “yoga pants” I would honestly like to know where the OP lives.
Now I have seen a lot of immodestly dressed women doing Crossfit, but that’s a different thing.
Seconded.
What’s funny is gallows fodder’s response was entirely reasonable and suggested that maybe some women wear them to look good but for her it’s for comfort. But that was sufficient trigger for the OP.