Businesses prefer tipping because they don't need to provide benefits or scheduling for their employees. When they are slow, they aren't paying for all the staff hanging around. When it is busy, they still aren't paying their staff, but they have even more because people want to work for tips when it is busy. And when their employees act up, the customers are the ones who deal with it.
Tips let businesses staff for peanuts while punishing their employees with terrible schedules so they quit instead of being fired and getting unemployment.