Yes,, it depends on where you live, and in the South most earn less than minimum wage....tips are considered part of their pay and they pay income tax on a portion of them that they report...or used to. Some restaurants charge a 10 or 15% gratuity for the tip, but not all and it wasn’t policy a long time ago.
Tips diminish in hard times, so a gratuity helps. Each state is different I suppose.