From my point of view, gear and weapons are an MMO element of this game. Now I know destiny is not an Mmo, BUT there are elements of it. Especially because the gear is tiered from common to exotic (normal in mmos) in most games that follow this system, some weapons are left behind to be relevant in the content they were made for I.e: expansions before TTK. I know this won't be the case for all weapons as some are being carried forward but I for one think it would be boring to have the same stuff forever but I can see the other side where it would be cool to have an old weapon in a later version of the game and people ask you, wow where can I get that?! Just my humble opinion and I know it won't be everyone's but just sharing :)