Everyone involved in this business (delivery people, restaurants and consumers) are doing it on a voluntary basis because they are all better off.
Extra sales that doesn’t require service for the restaurant, extra cash for the delivery persons.. etc

I think this is an assumption—better off, or desperate?

You started by agreeing this service is awesome for the consumers.. How can something that does loads of good to millions be unethical even if restaurants are getting a bad deal (which they are not)?!

Many of the restaurants are getting a bad deal though.

I write about psychology, philosophy, and society. Also a part-time moose masseuse. Hit me up if you need me to de-knot your elk.