I don't know, for me, I liked the way certain exotics or hell even legendaries looked. Your logic and technically bungies makes sense in a rpg element... but here I'd like to take a page out of borderlands loot scenario. If i got a legendary pistol I could find solace in the fact that when I did outgrow it I could always find a more powerful version of it later! I don't mind diversifying my look when it's a choice I, the player, makes. But when it feels like I'm being forced into a change..especially for a game.. it just seems..distasteful.