It lets the owner continue to pay employees ahit wages because they don't leave to get higher paying jobs elsewhere. It is an end run around their obligation to pay a fair wage by tugging at the heartstrings of people who buy into tipping as a solution to underpayment workers.
Servers deserve tips as long as they have the shitty exemption to minimum wage, but someone working the register at a convenience store or even a batista at a coffee shop doesn't.
Do you tip underpaid janitors, cooks, delivery drivers, child care workers, cashiers at grocery stores, or fast food workers?