I must wear jeans for most of my cycling and have never had any real problems with them (Levis for what its worth). They do wear out on the arse (how do you wear the crutch out?), but then I line the arse and they go for ages. I've never done more than a 50 miler in jeans though - touring I of course wear padded lycra. Obviously if i'm specifically going on a ride as opposed to going from A to B for a purpose I'll again wear more suitable stuff, but in themselves they seem no less suitable than any other cotton trousers.
I must wear jeans for most of my cycling and have never had any real problems with them (Levis for what its worth). They do wear out on the arse (how do you wear the crutch out?), but then I line the arse and they go for ages. I've never done more than a 50 miler in jeans though - touring I of course wear padded lycra. Obviously if i'm specifically going on a ride as opposed to going from A to B for a purpose I'll again wear more suitable stuff, but in themselves they seem no less suitable than any other cotton trousers.