Trading between alts

[Nix]

Because if they did allow such a thing, demand for paid retainers would plummet.

This is basically the primary reason imo

I'm feelin' it.

I would love to see a way to trade between alts - if they were worried about RMT, they could restrict the trading of gil between alts and only allow items.
I hate to endorse this, and do so begrudgingly, but if they are so worried about people not purchasing retainers, then make purchased retainers shared on the account.