[mort96]

I'm guessing at least part of the reason is that old school delivery driving doesn't have to be profitable, only the whole business does. If you have a healthy margin per pizza, that margin can subsidise the loss made per delivery. You just have to make sure that the profit from the increased number of pizzas sold makes up for the cost of delivery and you're good.

Food delivery services, on the other hand, have to make the delivery itself not only profitable, but profitable enough to produce a somewhat livable wage for the driver once expenses like gas and car wear are accounted for, and the whole company has to live off of whatever it can siphon off from what the drivers get.