What would take for someone to ask and question why those were disabled?
Not that I would like to rent any of them at current price and without offset of DIAS NPC, but still would be nice for some players...
EDIT: That feeling like when I try to get my kids to figure out do something on their own, as part of learning them to be more independent ....
I doubt that getting an answer as to *why* the "official" in-game ability to rent portable versions of the Mailbox, AH, and Bank will never be told or made public. It may have been completely forgotten by this time. However, it's obvious that someone, or several someones, looked through the lua code, found the UI scripts, and incorporated them into at least one addon, as well as making them public so they could be used in macros. I'm not interested in discussing or debating the relative goodness or lack thereof.
You can "purchase" the Convenient Mailbox on any day of the week from the Ruby Shop (cost: 50 Rubies, ten uses). Every so often, the CM, CB, and CAH are also made available during IS sales. I have several of each, but don't remember the packages they came in or what the cost happened to be (in Diamonds).
I would also like to point out that if Gameforge asked Runewaker--and that's what it would take--to remove or disable the lua coding for those three items, anyone who had either spent Rubies or Diamonds for those items, or who had "rented" them, would essentially be SOL. Their items would be rendered useless, and any Diamonds expended for "rental" would likely be wasted and I doubt that Support would refund them. Why? The player(s) used an unintended function in order to rent the service(s). Personal responsibility would rear its ugly head, no?
Be careful what you ask for. You might be terribly disappointed with what you end up receiving.