Lots of utilities are natural regional monopolies. For example, it would be unrealistic and uneconomic to have two separate water companies, each with their own

Lots of utilities are natural regional monopolies. For example, it would be unrealistic and uneconomic to have two separate water companies, each with their own separate networks of rivers, sewage works, water pipes, etc. The same is also true to some extent for electricity generation and supply, gas pipelines, and railway networks. (Incidently the railways in the UK were built by competing companies, which is why the network is suboptimally designed, with for example separate stations in a town or city that don't easily connect to each other.)