That's true, but the delivery people do not work for McD's. They do not legally work for the delivery companies (although practically they do). People that pay for delivery will not pay very much for delivery, generally less than minimum wage. They'll instead get the food themselves.

McD's is a franchise in the US. Franchisees set prices.

And it gets those without having to pay drivers (and technically even workers in most McDonalds’ restaurants since they are franchised), so why would they start?

Delivery and final assembly of food is not McDonald’s’ business.