Usually restriction is due to suspicious activities. Anything you did? 
Sportsbooks do restrict players due to suspicious activities, but that's not always the case and I am guessing it wasn't what op encountered. They restrict/limit players for winning too much which makes more sense in this context.Their shady approach has nothing to do on why a sports betting site ban players but the last thing that you said is the true reason for it.
Incorrect! They do restrict players if they find something shady related to them sometimes, but this doesn't seem to be the case with op.