SAB needs a shop inside it to convert baubles to Bauble Bubbles.
The fact that the player has to leave SAB constantly significantly decreases server load performance. It is unnecessary to have to move the client into a common environment such as Rata Sum. Instead if the transactions occurred within the SAB instance (the SAB lobby) there would be less people loading back and forth.
Bottom line is, it’s a waste of time for the player, and a waste of resources for the IT department. Think of a better way.