My guess is the existing delivery infrastructure in most of the US is too effective to allow drones to succeed here (yet). Someday that will change, but I expect drone delivery to grow fastest where roads and other distribution infrastructure aren’t available (which may include remote areas of the US). Once the tech is proven, it’ll return to displace incumbent tech.
Edit: To clarify, most people don't use this most of the time, because most of the time 24-48hour delivery is fine. That said, it is VERY convenient when you realize you need X today and cannot wait. Even with the shipping fee, an Amazon basics cables is often cheaper than a trip to Best Buy.
[0]: https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...