Why can't we create any name we choose? Why does it have to be unique and not a Username#0000

Blizzard and many other games have this system. Is there a database limitation or something? It just seems so unnecessary. I just started the game and that was one of the first thing I noticed. Its not even a problem in any other game so why should it be in this one.

It's 2024 and we're unable to choose what we want since they're already taken. It's already early access. All I'm saying is that there should be no reason for anyone not to have a username they choose since the problem has already been solved in other titles.