Originally Posted by
kraner
Short answer, because Production/Live environment. Anyone working in a software/gaming development can tell you that updates made to the live environments will sometimes mess things up, especially huge updates. Messed up things that did not occur on the test environments, because unlike test, live doesn't start fresh on cycles or pull only the data it wants, it just has to deal with the data that's there.
As for the messed up launches, as proven in Legion, sharding "fixed" that. Hardware/Software has limitations. Show me big a game that can handle hundreds of players in the same place at the same time.
Also what's the big deal, they're just some minor inconveniences that will get addressed in the following days. You're not going to die because of them or if you don't play wow for a day. Relax.