The most general reason for us to be an account would be the violation of our ToS. (Link) Again, make sure to read those carefully.
If you're streaming mature content without having turned on the required filter, we might have to ban you. Of course we will try to contact you first before banning you without warning, so be sure to check your chat regularly.
Another reason could be, if you're streaming games without using gaming mode. Again, we try to contact you before we do that.
Of course users who stream copyright infringing material, harass and spam are being banned without trial.