When I first started running, I had no running clothes. I was 37, entering some sort of midlife crisis stage, and hadn't run since I was 14 or so. I ran track as a kid in the 80s, and all we had were these little cotton shorts and a regular t-shirt.
We wore those things over our underwear, just like regular shorts, so I didn't think twice about throwing on my cargo shorts and running around the block as hard as I could. Because the shorts started to sag a bit after running, I would also wear a belt. Sometimes, when it was hot, I would also take off my shirt despite the gut I had at the time.
I'm not sure how long I would have gone like that if it weren't for my wife, who took it upon herself to get me some running outfits. I shrugged my shoulders and donned my new "fancy pants" and joined the rest of the crowd.
To be honest, I never had any major problems running in cotton socks or cotton underwear or whatever. I think the new wicking materials are nice, but I still run with cotton underwear beneath my shorts. Now that I run longer runs, though, I have to wonder if there would be some serious issues with chafing and the cargo shorts.