American tipping culture exists in the service industry because the base wage is not livable. Yes, tips should not be mandatory. But first you need a livable minimum wage or otherwise "tipping" is not primarily about rewarding outstanding service but about making sure they can eat.
I agree with you fully. The fact that certain states are still so far behind with paying a wage under $3/hr is archaic and needs to be shamed until it is brought up with federal/region standards.
That said, the biggest problem with most service type employees right now, and this sadly gets away from DD, but is the amount of hours they are being given to work. I know many people who only get 12-18 hours a week at their service job (and even worse, you can be sent home early or even called off if it's slow), and even in CA where minimum wage is $14.25, one cannot pay rent let alone earn a living or even hope to have or provide for a family.
Quality bartenders generate increased revenue for businesses by either being more efficient and/or driving additional business. If a bartender excels at their job this can be objectively measured and their pay rate increased vs their peers as a reward.