Taking characters that may have already progressed quite a bit and bringing them to a new server where they'll have a pretty big advantage over freshly rolled characters isn't exactly great, either. A whole guild could transfer over to a fresh server, bringing a mountain of materials with them, allowing them to functionally control the entire economy on the server for a bit, if not quite a while.
Amazon has to think of the longterm health and stability of servers/the game, not just folks who don't want to wait in queues for a few days around launch. They're looking to the horizon, players are looking at their feet.
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RIP in pepperoni, my condolences. On the bright side at least there doesn't appear to be any streamer queue priority or anything, so they're stuck in the same super-long queues as everyone else. Which...will be worse since they're bringing their followers to the server clogging them up even more -_-