It's standard fare in the industry because it keeps server populations stable and, like charging for name changes, encourages accountability.
Also because it earns them more money.
It's not "these days" and we're not "kids" - you're trolling, or otherwise a kid yourself, as that's been a standard thing to be charged for since MMO's before World of Warcraft. There is no reason during normal play to swap between the US and EU servers with one character, and there's no need to change your character name either- unless you want to say, antagonize a whole bunch of people and then keep doing it anonymously.