You could make just as good a case that it’s the other way around.
A salaried employee makes the same amount of money whether they please people or not. Since pleasing people does not earn them extra income, they often won’t do it, and often their jobs even specifically require being an asshole (managers, supervisors, etc.) at least some of the time.
Someone who works for tips on the other hand can increase their pay quite a bit by pleasing people. And many professional assholes will actually tip quite well for good service, because being around other professional assholes all day can be quite tiring, and being generous for a change is a good way to unwind from that.
You could make just as good a case that it’s the other way around.
A salaried employee makes the same amount of money whether they please people or not. Since pleasing people does not earn them extra income, they often won’t do it, and often their jobs even specifically require being an asshole (managers, supervisors, etc.) at least some of the time.
Someone who works for tips on the other hand can increase their pay quite a bit by pleasing people. And many professional assholes will actually tip quite well for good service, because being around other professional assholes all day can be quite tiring, and being generous for a change is a good way to unwind from that.