I agree it's not really a tip, which should be purely optional. Unfortunately it's not treated that way in most of the US, where "expected tips" are allowed to

I agree it's not really a tip, which should be purely optional. Unfortunately it's not treated that way in most of the US, where "expected tips" are allowed to be treated as a part of the employee's compensation. The employer/employee wage negotiation should be completely independent of any tips and the employee should be receiving a wage they would be happy with even if they got 0 tips. Any tips should be in addition to that.