Guys are naturally attracted to a womens private area down there, and that includes panties. So yes, most of them do try to smell them. As for girls smelling their own, I've never really thought of that, unless they were lez.
Wow, who would have thought that such a harmless question would elicit such discussion! I like girl's panties of course, but wouldn't think of smelling my own underwear (unless I'm making a laundry decision). joking.
Because it is a somewhat forbidden/taboo practice, any hot bloodied male will sniff a woman's underwear wherever he gets a chance. Even if the smell is not particularly 'nice', he may well go back for a double take. I think it's just natural. Similarly, I think it good practice for a woman to sniff her own from time to time in order to be mindful her health and natural balance. Like checking the toilet roll after you've wiped your back side, it's perhaps instinctive and nothing to be ashamed of. An interesting debate I plan to follow up with my girlfriend.
Only if I think have a problem with my vaginal discharge i.e. it looks odd in color, or it itches, in which case I do it because I think I may have trust or a yeast infection, as most girls do from time to time.
That is unsanitary. I could understand a guy doing it because guys love anything that reminds them of getting laid. But did you know that underwear fibers have remnants of feces eww and that's what your putting your face into dirty girl lol! Plus the vagina naturally has bacteria and yeast...why this fascinates you so much...I do not know. Maybe you need to get a hobby?