The research is clear the the tips have very little to do with quality of service, and much more to do with who the customers are and who the servers are. More

The research is clear the the tips have very little to do with quality of service, and much more to do with who the customers are and who the servers are. More, waiters getting low tips tend to think their customers are cheap and not that their service was poor. So when he says that this doesn't happen it's a claim that is well supported by research.