Constantly because all underwear I've worn in my life I found uncomfortable. Not in *that* area but tight around my waist. I'm just used to not wearing any so I don't feel compelled to. Does mean I need to keep a closer 'smell' check on my trousers but all in all, I don't find it bothering. Hell, least I don't wear my trousers hung low like my scrubby peers.
Does mean I was unfortunately unable to take part in the hilarious game of 'pulling people's trousers down' growing up.
I also don't like wearing socks. I find they're unbearable to wear. Suppose I'm just hyper sensative to touch.
I never caught myself on my fly. Because I'm not stupid and, tuck it in, before I do it up. I've evolved to not wearing underwear.