Of course there is an urban advantage to services like this. In high density areas, the economics of the delivery service can make financial sense.
This isn't sour grapes, I probably wouldn't use the service anyways.
But consider this, the Bay Area (the premier delivery zone) has less than half the density of my town, which is on the edge of the principle tech corridor of the entire East Coast, which carries 70% of all the world's internet traffic, has more telecom and satellite companies than any place else on the planet, the national hub for data storage facilities, relatively low taxes, the highest educated and most affluent workforce in the U.S. and an astonishing number of high density business clusters.
If you consider the metro area I'm in (D.C.), the metro area is almost exactly like that of the entire Bay Area. Similar area, similar population density, centered on a major city with a similarly sized population. Both have extensive traffic issues, highly educated, affluent and mobile workforces, etc. Arguably has better transit infrastructure, logistics infrastructure and other supports. We also have far worse weather, making a service like this make far more sense.
But as we've seen time and again, the Bay Area desperately wants to be NYC (or rather, Manhattan) yet has characteristics no better than a #10 metro area and is only willing to take on the Bay Area and just one borough of NYC. San Francisco itself is just #20 in terms of density and only 1/10 the population of NYC.
SV needs to start acting like there's more to the U.S. than the Bay Area and Manhattan. I can almost guarantee that if it comes to my metro region, they'll center it only in D.C., it won't do well (because of the regional demographics) and once again the D.C. metro region will miss out on some of these interesting consumer offerings because nobody from the West Coast can be bothered to learn about different places.