Restaurants have a lot of competition, and low margins. Like any other employer, they can offer jobs at low wages (or at least could, until the government got involved). People are under no obligation to accept a job with low wages, but some do. By definition the employees are not slaves, because they can quit at any time.
Employers offer wages that the labor market will bear. Some jobs are mostly unskilled labor, and the pay is appropriate. Restaurant workers get tips, and I am usually very generous. Apparently tipping has become much less popular lately.
Notable exceptions to skill vs. wages include things like the Longshoremen in the Port of Los Angeles, who belong to a union that extorts the shipping industry. There is no justification whatsoever for the high salaries they earn.
> People are under no obligation to accept a job with low wages.
This is the wrong premise you are basing your entire conviction on.
When you don't have an alternative to working then it is not a jobmarket as you are not in a position do not transact.
This is the same reason why the housingmarket is not a market the second people do not have alternatives to buy into overpriced rents.
A free market requires that participants can decide not to transact. A pro-market government makes sure that this is is the case to a reasonable extend.
