The unit economics in the US just don't quite add up. Assuming in a rational market a driver has to make about the equivalent of minimum wage (or else they'd take a less taxing minimum wage job) they need to make say $15 an hour in SF. So if I order a Cheesecake Factory from Union Square to the Marina, they arguably will take 30-40 mins roundtrip, so even at full utilization, the delivery is costing nearly $8. Unless the delivery fee is > $8 then the margin on food subsidizes the delivery which seems like a pretty rotten strategy to lower margins even further. Theoretically I guess they could do point to point delivery where they then pickup in Marina but that seems far more difficult and anecdotally never the case when I ask a driver. In that case you could assume a one way takes say 20-25 mins (waiting on delivery probably adds 5 to each order), then that's still a $7 delivery cost at the margin.

One can make the case this can be made to work in dense cities say 1m or more with a density over X people/p. sq. ft. like in Europe/Asia. But I don't think there are many US cities with this kind of density to support.