The federal minimum wage for servers and other tipped employees in the US is $2.13 per hour. I don't think it's increased in literally 40 years.
some restaurants have slow days, and the waitstaff doesn't have a choice. They get minimum wage because there are no tips, or there are so few customers as to make the tips meaningless vs the hours spent.
However, as noted previously, that sub-minimum wage is "before tips". If, over the course of a week (iirc), the waiter makes less than the actual minimum wage ($7.25 federally), then the employer must make up the difference. That being said, I would guess any wait staff that go this route on a regular basis don't wind up employed for long.
some restaurants have slow days, and the waitstaff doesn't have a choice. They get minimum wage because there are no tips, or there are so few customers as to make the tips meaningless vs the hours spent.