You shouldn't go to restaurants at all if you're averse to tipping. Only by starving the industry can the policy be scrapped. Don't take it out on the workers. Hold the owners to account.

I'd say it's a little thornier than that. By tipping, you support the person who has to take the job that doesn't pay them a living wage. Absolutely, this can have the side effect of supporting the system creating this condition, but so too does patronizing businesses that employ this practice. The best move if you don't want to support the system is to not patronize businesses that function this way at all. Increasing corporate revenue while not contributing to the welfare of the person who had to take that job is not a morally better position.

Feel somewhat similar about giving money to beggars, though with slightly more emphasis on the voluntary nature of the act (which itself could be fodder for moral discussion - what's the difference between Jack the Hobo's and Jack the Barista's experience?). End of the day, while systematic overhaul so both of these conditions are irrelevant is warranted, for both groups it's about survival until the next day (yes, for some beggars survival includes dope, withdrawl is hell). The revolution ain't coming tomorrow, and even if it did there's time required to get these folks what they need. It's entirely possible they wouldn't make it to that point without voluntary support from individuals or small groups.