I believe servers are in the same cluster, there is no bandwidth limitation etc. The real reason (guess) to balance servers population, some servers are really empty like Mateus server back in Sept 2014, it was almost dead on peak time. Now it is very populated. It will open again soon once all the servers population are equalized.

The login queue, prevent connection flood, putting load on the login/auth module of the server. Just 2 cents...