This allows him to also be able to change suits (like if he decides to make one with the Kingdom Come symbol or not). The alternative origin that it is merely from Krypton could also make sense (even if it is a lazier justification, creatively speaking, to just say that that's how people dressed on his world), in that the classic Superman costume look-- "undies" and all-- is just how people dressed on Krypton. Either way, there's no reason why the suit would have to be altered from the way it is supposed to look. The likelihood that there are aliens that would dress like the classic Superman costume is about as likely as there being aliens that are humanoid in appearance, the "realism" argument is moot either way. It's just the latest pretentious pockets and pouches/leather matrix-y outfit trendy junk from Jim Lee that has infected everyone. Also, armor for Superman is incredibly stupid. He's Superman. He doesn't need "invincible" armor. I get that armor is all the rage now because of the success of Iron Man and the recent Batman movies, but not EVERYONE NEEDS armor because it's what the most popular characters are wearing, and characters like Superman, Green Lantern, and Flash especially don't. It's almost the same thing in Wonder Woman's case: rarely is the armor itself actually able to keep up with the wear and tear that Wonder Woman herself can, and almost always ends up being broken and ripped off in a fight. So it would be with Superman, but worse. The aura/Kent created Superman identity works best for this reason, rather than the "predestined god" sent here to fulfill his father's destiny junk that basically dehumanizes the character.