On the other hand, it also gives the consumer more power over the wages of an employee than any other business. Do you think your fast food or retail employees are under paid? Teachers? Fire fighters? Too bad, you have almost 0 power to change that (and some of those positions have policies / legal prohibitions from accepting tips at all). But your local restaurant servers? If you think they're not paid enough, you have the direct ability to make a change on that front. Sure you probably still need to convince everyone else to do it too, but on the other hand, we can see that working in the fact that the "expected" tip rate has risen over time from ~10% to ~20%.
In fact, now that I think about it, since tips are a percentage of the bill, I wonder if tipped wages keep place with inflation better than retail?
Not to say that this is a great system overall, but I also find the mindset that's worried about tipped wages to be odd, because like I said, if you think they should get paid more that's entirely in your control. No one needs to wait for the boss to decide to hand out raises or make market adjustments. And most of my friends who worked tipped jobs weren't bothered by the tips per-se as they were with the times when work was slow. Sure they griped about stingy tippers, but none of them ever had a top complaint of "man I wish I could just make $8/ hour flat rate instead of getting tips"