[tshaddox]

I would imagine it's for the same reason that many big musical acts go to lengths to make it difficult for concert tickets to be resold. It's important to them to manage their relationship with their customers, and they simply don't want all or most of their tickets essentially being auctioned off to the highest bidders even if that is technically the most economically efficient allocation according to some extremely short-sighted interpretation of an Econ 101 textbook. Heck, it's the same reason Apple sometimes has long wait times for a new popular iPhone model instead of holding an auction and shipping to the highest bidders first.

[ricardobayes]

I think you're right, it's what separates companies classing the same/similar behavior as unwanted, even illegal (grey market luxury watch dealers) vs encouraged (food delivery). The relationship with the client and it's perceived value. Coming to think about it, probably a Michelin-star high-end restaurant would shoo away a doordash person coming to pick up takeaway.