[tvh]

Good point. To answer your question blatantly: by law. Not saying "you can't ever tip". But more to frame the employer/employee contract and prevent the employee relying on tips, and instead having a contractual/legal framework for his salary.

Let me be clear in saying however that I'm not a fan of shaping culture changes by legal requirements. So I'm second guessing myself a little too now, but I really think the culturally accepted tipping expectation is detrimental overall as per my original comment.