>>534200541
In the past you could queue ranked from anywhere as long as it was (you)r home server, but because not many people actually play ranked, this just lead to every season having the same 10 names in the leaderboard and queues dying in a month max.
So they made it so everyone has to queue on one server so queues stay alive longer.

There is a hint of irony in m saying this though because I hit diamond and now ranked is dead again.