I don't know everything regarding the game's innards, but I do know that items when created have a unique ID and they're created on that server. There's a lot of complication when something goes wrong in a character transfer or something else. I once transferred a character of mine with all my BoA's on him and then mailed some of the BoA's to an alt I had on the new realm that just so happened to have the same name as an alt I had on the old realm. The items ended up on that character even though this was 2 weeks after my transfer and I could not get them back over to my new realm toons. It took GM's a couple of weeks to fix it (not to get to my ticket... the ticket was answered in 3 days). Ultimately, they were able to fix it, but it was really hard for them to move just the items back. Creating an in-game interface that could do this tech would be even more complicated, I'm sure. We just need to be patient. Like a lot of ppl have said, it's low priority and a pain to implement.