Waiting time for the next order is the same distribution for each one of them. So to minimize the number of pay gaps in a day, you will want to stretch out each

Waiting time for the next order is the same distribution for each one of them. So to minimize the number of pay gaps in a day, you will want to stretch out each delivery as long as possible. If you are a true believer in the impossibility of good service in the absence of heavily tip-based pay, you set up incentives like this and your belief system won't ever be challenged.