Never worked as a server, so what I have to say is only based on what I've heard other servers say, but I think I have an explanation.
At least in some states, servers are theoretically required to report the amount of their tips to their employers, who then withhold based on the total of tips plus hourly wage. If they earn enough in tips, the total amount of withholding for all taxes, federal, FICA, SS and state, if any, could easily amount to more than the $2.13 they earn hourly. (BTW, that $2.13 is a federal minimum, some states require a higher amount than that.) In such circumstances, the check the employee receives would be zeroed out, but it should reflect the withholdings that the employer makes on the employee's behalf.
Ridicule is the only weapon which can be used against unintelligible propositions. Ideas must be distinct before reason can act upon them; and no man ever had a distinct idea of the trinity. It is the mere Abracadabra of the mountebanks calling themselves the priests of Jesus. -- Thomas Jefferson
For we know that our patchwork heritage is a strength, not a weakness. We are a nation of Christians and Muslims, Jews and Hindus -- and non-believers. -- Barack Obama
We see monsters where science shows us windmills. -- Phat