"You can't really support two competing sewage treatment plants because how are you going to route the waste to the one you choose without a whole separate network of pipes? Likewise with water, electricity, or gas."
In Texas, they deregulated electricity almost 20 years ago. It caused a bunch of competing "providers" to fight each other to give the best rates. The electricity itself is provided by the local TDU (Transmission and Delivery Utility), which is kind of like the government. They charge a very stable base rate, and the providers will usually pass that through plus a few extra cents for kWh to keep their business going. Ultimately, the provider just handles the "paperwork" side of things. If you have any trouble with the electricity, you contact your TDU.
All of this is not available for everyone (such as more rural areas), but it did greatly increase competition for many.