My apologies as that is not at all how I read your response.
When I was attending college you were paid a minimum serving wage plus tips.
That minimum serving wage + tips had to be greater than or equal to the minimum wage for the area.
If enough tips were not made the restaurant would have to pay the server more to get them to the actual minimum wage.
Restaurants love servers as they make them do extra work without having to pay them for all of the extras as in the end the customer ends up paying them. It is rare that a server does not meet the official minimum wage for their area.
Obviously times have changed as
@tvguy pointed out in CA they must make a minimum of $16 PLUS tips.