Isn't it just about manners? I mean, I wouldn't want to see a loving couple groping each other at the belay station, wouldn't want to hear someone discussing the runny boils on their genitals, wouldn't want to see somebody take a crap in plain view. Plain old social conventions make it so I don't have to see it and know not to do it. At the crag, though... some people climb just to get that fuck you world feeling.