But on the flip side of this, people who like to roll alts (for reasons of variety, or perhaps to be incognito for an hour or two every so often) can not easily mail stuff between alts. I know you could ask nicely and perhaps your FC will let you use the vault to transfer (assuming both alts are in the same FC), or parhaps getting someone you trust to be a middle man. It's still not ideal in both scenarios.