Why to wear an underwear, or why not?

I’m obsessed with underwears, a boxershort or anything that keeps my crotch in place. Yesterday I bought 2 pairs of cotton low rise fit boxer. It was an offer on sale and I just thought, do I need them? I had more than 10 sets of not-a-really-old pairs but do you think I’m sick that I had to keep buying them? I am quite fond of boxershorts and besides being comfortable they are also very stylish.

Do you go for the brands? Do we buy and wear them because the ads catches our attention? What function does underwear serve for men or for women? Is it strictly a cultural thing? Does it offer any difference in hygiene, given you wear your pants only once?

Guys, what is your favorite kind of underwear to wear? If you are a girl what is your favorite kind of underwear to see on guys? Which ones do you think based on your taste, is sexier? A boxershort, a tanga, or the plain white classic underwear?