it all boils down to a few factors, if your asking "why no hair" its either, shaving or doesn't grow for them.
if your asking "why shirtless" probably because their either, comfortable that way, trying to show off for the loose women/men if they swing that way, because the sun sucks and is trying to bake us inside our own clothing.
I frankly am Italian, there is no remedy for our hairs potential, and I just to happen to be proud of my unstoppable human fur that is honestly almost as strong as metal, Fing takes an hour to merely trim my head with top of the line buzzers.
Also, for those that say a shaved chest is sexier, that opinion is best left to the wife/husband to be, Same rule applies to potential epicness of beards, while I've not heard of a couple separating purely because of facial hair, anyone that won't accept your beard if you've chosen to be so bearded, can return to the shallow end of the pool.
(People, you don't have to be creepy furry to like a hairy bulky mountain man, thankfully, because i'd have been alone forever lol!)
I, I am a Yeti, and that ain't changing.