Earlier quoted context omitted.
Mojang would have a problem trying to control Minecraft because it's written in Java, their developers commonly associate with the players who hack the game, and the only control over the gameservers that they have is their authentication servers- which you can disable the use of by editing one flag in your server config files, allowing anyone to play even if they didn't buy the game.
But then you have absolutely no authentication whatsoever. So anyone can join your server using any player name and it's difficult to effectively ban. Good maybe for small private servers, but won't work for anything public. Also IIRC then you get no user-selected player skins.
There are other ways. For a while, I played on a private Minecraft server which disabled authentication (for reasons; that server also had the mod which allows Bedrock players to connect to a Java server, which probably played a part). However, once you connected to that server, you had 30 seconds to type a command with a password, otherwise you'd be kicked out, and before entering that command, the player is frozen and has no access to the inventory. The closest analogue is IRC's NickServ.
That server also had a way to allow everyone to use their own user-selected player skins, even without authenticating to the skin servers, though I don't know the details on how that worked.