Businesses in local have two-sided network effects. The most famous two-sided network effect is eBay, where the buyers attract the sellers and the sellers attract the buyers. Here you have local businesses and consumers as the two sides. Ideally, you would have long-term, exclusive relationships with the local businesses and offer some loyalty rewards to the consumers.

There are also some interesting scale economics unique to logistics. It doesn't cost much more to deliver to two houses on the same street vs. one house. So as the density of your userbase goes up, your cost per delivery drops. That being said, scale advantages of local delivery do not approach the scale advantages of a wider network like UPS/FedEx. If delivery were the only aspect of the business, I agree that it would be very competitive

Although I do believe local delivery companies are defensible, they are not necessarily a winner-take-all business in every market like eBay or craigslist. Multiple delivery companies can coexist in a local market, each serving a distinct set of restaurants