Glamour Dresser Update - Why so little?

[Penthea]

But they servers can handle extra retainer info?

You can't use retainers when you're not in your home server.

Also retainer info is likely stored differently because you don't carry retainers around with you. You need to access them with the summoning bell, so that is when the information is requested from the server. Whereas for things like glam plates and your personal inventory, all that is constantly carried on your character. When you visit another server all that info your character is carrying needs to be tracked.

The reason why we cannot access retainers on other servers has something to do with how that information is accessed (retainer info is tied to servers, likely a side effect of how selling on the mb works) rather than world visiting itself presenting a roadblock.