The main reason is that they are member owners of the system. When they drive down the road, they can say, “I own that power pole.” Also, the rates, in most cases, are less than what the utility company is paying. It's an investment in the future. They look back, and some of their grandfathers or fathers or uncles helped to physically build the system.
It's also self-financed. A lot of people, including, put up their own money. They lent money to their neighbours in order to start it. There's a lot of pride in it.
The only thing now, as I said before, is that they're a plum; somebody wants to buy them.