the rest is supposed to be made up in tips.
However, tips are not mandatory. That system is flawed and since you volunteered for this job, knowing that it is flawed, you have no grounds to complain.
Change your workplace. Waitressing is an entry level position, so try some other entry level job that offers more secure earnings.
If enough people leave the waitressing field, the pay scale will be re-approached in order to attract people to fill the hole that was left.
Bottom-line, complaining about a voluntary act by a customer in a job field that one willingly sought out, is really really self-centered and just dumb.