Is it just me or where I live, but is it becoming less acceptable for men to go shirtless?
When I was more of businessman and less of a roofer, I'd keep my shirt on. Now that I am on the roof more, the shirt goes flying off rather quickly. Altho I am slim and don't have a beer gut, (I used to) it's a comfort thing. In mixed company, life in general, I always wear a shirt except at the pool or beach. Most men don't need to take off their shirts... the gut is already highly visible.
( I see it with the women too..... in general America's physical shape is poor)
I don't see men shirtless often either. I don't really know how much it's changed from before other than the risk of sun exposure, like some have mentioned, and perhaps the fact that a lot of outdoor labor jobs are more mechanized - which was where I think it seemed more prevalent