Bosses are legally required to make up the difference to minimum wage if a tipped employee doesn't get enough tips.

If I tip a cashier, then we're taking money away from the working class to give to the working class, which means there's no net change. But if I refuse to tip, the boss has to make up the difference and the working class gets money from the capital class.

Therefore tipping is class treachery. You're depriving the workers of chances to take money from the bourgeois.