The restaurant did not hire them. DoorDash is a third party. As a matter of fact they will just pull menus from restaurants and put them on their app even if the restaurant does not offer doordash. I know this because they've tried to do it at our establishment.
Occasionally, we'll get DoorDash delivery drivers coming in saying they're here to pick up an order that was never placed because we don't use those apps and it was done using an old menu so we couldn't provide them with that food even if we wanted to.
The only way to get to go food from our restaurant is to call up and place your order and come pick it up yourself. We're more upscale and we're not trying to crash our kitchen with to-go orders when we have people spending hundreds of dollars in the restaurant.