You prefer your "men in combat to be wearing a t-shirt and shorts"?
Do boxers wear t-shirts? Do UFC fighters wear T-Shirts? When have "men in combat" worn t-shirts? Did you just start watching wrestling when Kevin Owens debuted? Prior to Kevin Owens, name the championship-level wrestler who had to wear a t-shirt because he looked like he was 7 months pregnant. And don't give me Foley, he was a transitional-type champion, they threw him a bone as a "lifetime achievement award" of sorts.
Yeah, and wrestling used to be conducted in the nude. Should we go back to that? Because if you are looking for a more traditional look, that would be the look to shoot for.
I would have even less interest in pro wrestling if everyone was just wearing the same ol' boring-ass spandex trunks. The variety of attires and how it compliments a wrestler's character is part of what makes pro wrestling more interesting and engaging.
No boxers don't wear t-shirts, or UFC fighters but those are ACTUAL sports with strict regulations. Clothing restrictions would be due to wanting to take away any actual sporting advantage or disadvantage from someone wearing a t-shirt or other type of additional clothing.
Pro wrestling may mimic pro sports but if it wanted to be more true to it's 'amateur' cousin then every wrestler would be wearing a full body spandex singlet. It would be more realistic but I'm pretty sure characters like Undertaker, Mankind, Jeff Hardy, Bray Wyatt, Dean Ambrose and many others would lose a significant something in their appeal if they didn't wear their signature ring gear.