As things are now, the restaurant pays a base wage (usually below the federal minimum wage level) and lets the servers keep whatever tips they receive.
Managing the marginal labor pool -- unskilled workers who earn minimum wage or slightly more -- is a perpetual problem in the fast-food and hospitality industries.
That's 7 cents using the black market rate, which doesn't sound like a lot, but still amounts to about a half-hour of pay for someone who makes the minimum wage.