Sponsors usually only do that if the affiliate really stands out as one that's losing a ton of money... If the sites are doing fine overall and they don't feel they need to do anything better with the members areas there's nothing wrong with cancelling a destructive affiliate.... as long as it's in the terms and conditions.
Payouts are so high these days there's nothing wrong with having expectations on how the sites should perform. If an affiliate does terribly below average, time to clean house.
