The reason they won’t remove login realm selection as a visible thing you can interact with is naming conventions more than anything else. If not for that they could have already hidden that aspect of the game from us when they did the warband revamp and showed all our characters at login from all realms.
They would have to change naming conventions or allow names with spaces or first and last names or something if we didn’t have the same “unique” names across dozens of servers. Then they’d have to have the entire playerbase re-name their characters.