A Model / Broadcaster can ban anyone from their room, they don’t need a reason to ban a user from the room.

But normally a user will be banned for the following:

Disrespect,

Trolling,

Posting disgusting images,

Spam,

Not listing to rules of their room, not listening to moderators (if there are any)

or Just sitting in their room and not talking

It can also be a case of they may of banned you by mistake.