I generally ride 7 miles to school and work up enough of a sweat to shower and change. Well, just for kicks, I decided to ride home one day towards the end of last semester in my regular cotton shorts. The temp was low enough and I was taking it easy so as to avoid working up a massive sweat. I tried to just take my time, find a slower route, and just enjoy myself. In the end, I got very mildly sweaty, but enough that I didn't need to jump in the shower. However, my crotch got some heavy chaffing and consequently really dry skin afterwards with lots of shedding of skin for a few days. So yeah, cycling shorts for me, please. Or at minimum, a synthetic short liner with a pad.

So while others can get away with it, for me and my nether regions, cycling specific clothes are preferred.