Aquaman and Namor are both adapted to the harsh environment of the deep sea, which I guess would make you strong.
Wonder Woman is a God, so she gets a pass.
Captain America got super soldiered so he gets a pass.
Green Lantern shouldn't have muscles as his whole powers are mental. Cyborg too.
Martian Manhunter is a shapeshifter so he'd just make himself aesthetic.
Red Tornado and Vision are robots so they were built to be aesthetic.
Iron Man and...