I now have a possible explanation
I used to wonder about that too. I'm female, but grew up sharing a bathroom with two brothers and quickly learned that there are bigger things to worry about than whether the seat is up (like whether the floor is wet). Personally, I'd rather they left the seat up than didn't put it up at all (and left the drips for me to wipe up). So until recently I really couldn't care less.

However, I now live in a small apartment with a very small bathroom, as do most of my friends. This generally means there's some form of storage above the toilet and I have quickly learnt that the lid is there primarily to stop things like hairbrushes falling in.
(xanthine, Sun 3 Jan 2010, 21:59, Reply)