> stop looking at the customers as walking wallets

Maybe that would help if the salary was enough to be self-sustaining and tips weren't necessary to make ends meet.

Also, it's a vicious circle. It's harder to be nice to staff when they're not pleasant, it's harder for staff to be pleasant when their customers are brats with copious self-entitlement and condescension towards service workers.

Empathy goes a long way here.

> 99 % of the time, it's the staff's fault

If that's your experience, I'd try looking inwards to find reasons why as well.