Please buy more retainers to alleviate the inventory problem - Yoshida
Not his actual words as that would be a PR disaster but that's literally the best we've got, it's always PS3/server limitations, the servers will explode if we give everyone free retainers, etc. I remember reading pre-Heavensward (or maybe it was a recent interview, I honestly can't recall) that the majority of players haven't even filled their first retainer's inventory, so it's likely not a high priority either.