I'm not talking about about t shirts that are tight, i'm talking ones that are fitted. This is styleforum, no? An added benefit of a well fitting t shirt is that it accentuates your physique.
As far as your last point, not true at all. I'm aware that i'm really not that big in the grand scheme of things, but at the same time, i've put in work for the body I do have, and I don't think there is anything wrong in trying to flaunt it a bit.