Their business isn't food delivery but food distribution. The restaurants are paying for a spot on their webpage (some of these companies don't deliver, and charge the same price i.e. Just Eat).

I think this idea does apply to any model where the distribution/search costs are minimal i.e. Uber/Lyft. I think Lyft is a great business btw but their costs are totally wrong (i.e. they don't really need hundreds of software engineers milking the company dry).