Utilities in the US are generally considered natural monopolies. That is, it's unreasonable for a competitor to build duplicate infrastructure to compete. The costs are too high. Only one firm can really provide the service to a market.

As such, they're highly regulated. Prices, staffing, availability, quality, etc. are all highly prescribed by the local or state government.

So why not make them government owned? Well, it's a trade off. Public utilities tend to be less innovative and have less of an incentive to invest in improvements. Private ones have less of an incentive to provide stable, low prices and service.