minimum wage for industry with tips is 2.13 an hour and the IRS estimates how much tip you make and taxes you that amount. Not tipping simply robs the worker.
I have plenty of problems with tipping culture, but this one is entirely of the server's making, and is a common trope.
If you can demonstrate/document less tips than the IRS estimate, that's exactly what you will be taxed. Nobody is forcing you to be taxed on unearned income...
... but most servers don't do that because the vast majority of them make entirely more than the IRS tipping estimates.
https://www.irs.gov/businesses/small-businesses-self-employe...
Fill this out every month: https://www.irs.gov/pub/irs-access/f4070_accessible.pdf