Hehe, that's the big difference though right? We already have a really efficient, profitable delivery infrastructure. It just doesn't do near-real-time deliveries.

You can have fast deliveries, or you can have efficient/full-utilization of delivery workers. Even in a place as dense as New York City it's still very difficult to aggregate enough deliveries together that profitability for workers becomes substantial. Most are running around with 1-2 deliveries at a time.