Why couldn’t we just have a super server with everyone for NA. They would have to eventually be merged anyways as people will flock to the most populated servers and empty servers will just keep dying out. Or just one big East and West servers? Why all the sub servers for?
So from my understanding the reason is done by most games is the “servers” are more or less server clusters, without getting too technical, more servers in a cluster = more potential for problem. So the way to get around this is to have multiple clusters of servers so if one goes down then you can work on it while only affecting say 10% of the player base vs 100%. You COULD also allow people to login to clusters as they see fit but then you have to worry about data synchronization between the clusters at that point and that brings in an entirely new level of “lets hope this doesn’t break”.