A combination of tipping and converting jobs that were typically held by blacks to unpaid positions provided a solution. It became popular despite attempts to ban the practice.
Today, tipped workers in the US are paid, but have a lower minimum wage than normal workers.
Source: https://time.com/5404475/history-tipping-american-restaurant...
FWIW: Because I abhor the practice, I always tip 20%. If service is sufficiently bad, I tip 20% and never come back.