"visit another world server" from login screen - what is the point?

[KarstenS]

It's so you can log in during periods of high congestion - patch days sometimes, but mostly expansion launches. The randomness is to help spread the server load.

Another reason is if your server is congested, then you can transfer to a less congested world this way so you don't have as large of a login queue.

It's intended for periods of very high log in congestion, like an expansion launch.

Last times I tried it for exact this reason, an error message popped up that told me something like this feature cannot be used due to high congestion.