Whenever I wear leggings or yoga pants I always go for a seamless underwear or a thong but I noticed some girls do not. (No I do not spend my time watching other girls butts) I was just curious if guys actually noticed or cared. Or if other females judge or notice others for the underwear line. I never knew it was such a big deal until my cousin (who is a complete idiot) was like "yeah I make fun of girls for the lines when they wear the wrong underwear"
I seriously just saw some girl the other day and she was wearing leggings she looked cute but i didn't see any panties line , i didn't see any thong line all i saw was her black leggings her leggings were form fitting too and I'm not a creep who looks sexual at girls.
Whenever I go to the gym, I can usually spot what types of underwear the women are wearing under their yoga pants. Sometimes, their yoga pants do get a little transparent and their thongs show. Not all of them are skinny and I'm okay with that.