User blog comment:ZanaLyrander/Thoughts on Legacy Skins/@comment-5819230-20130730220601/@comment-11759251-20130731122711

See, I can understand rewarding long time customers, giving them the satisfaction of knowing that they have a skin few others have, but that's a double-edged sword, because it also sends a message to new players. It's like saying "hey, check out this really cool skin! Do you like how it looks? Do you want it? Too bad, you should have started playing earlier." That isn't a message Riot wants to send to new players, as they certainly don't want to discourage new users.

The fact that they occasionally open the vault mitigates this effect somewhat, but they don't do that very often. It also artificially inflates the value of these skins, many of which are not very impressive by themselves, they are only impressive because they show how long the user has been playing, something accomplished equally well by certain summoner icons.