This is just what tips are. People (in the US) are used to tipping in restaurants but many don't realize that in almost every case the restaurant is using thos

This is just what tips are. People (in the US) are used to tipping in restaurants but many don't realize that in almost every case the restaurant is using those tips to top up the wages they should be paying the servers anyway. So the restaurant can pay the server much less than the minimum wage - your tips just make up the difference until the server makes some minimum. What DoorDash is doing here isn't any different except that servers usually manage to make more in tips. In conclusion, tipping culture sucks and the sooner employees start paying decent base wages the better.