It's because drivers can and will reject orders with $0 tips. Drivers with GH get paid $3 + $.50 mileage as the crow flies. A $0 left on an order will be a total pay anywhere from $3-$5 depending on distance. It's absolutely not worth it to drive for $3-5 per order especially when a round trip for that order takes around 30 minutes. Also we don't get paid mileage for the trip to the restaurant. To add to the fire GH, DD, UE, etc all take about 25% from the restaurant so everyone is losing except for the courier companies.