The comparison to DoorDash isn't table service in a restaurant, it's ordering food for delivery to your house and then giving cash to the driver. Where does that cash go? The driver's pocket. That process & the cultural understanding of it has literally been around as long as the concept of tipping.
Here's the real question that answers why people are "upset". If you did a poll of 100 people ordering on DoorDash, and asked them "when you tip on your order, where does the money go", what do you think people would say? 99/100 of them would ABSOLUTELY say "to the driver" and that is everything that is wrong with what DoorDash did. I struggle to engage sincerely in argument with anyone claiming otherwise.