That's true, but supermarkets compete with one another on price and other factors. They are motivated to do things to get more customers. Yes, there are many cases where supermarkets have been bad actors, but that's solvable with competition regulation. Water service is very different, and the current setup in the UK seems pretty insane - you can't have competition on who supplies water to your house. People aren't going to move location because of the quality of the water supply until things get very bad. They are motivated to spend as little as possible.
You can set up a system where companies are involved in the delivery of water in a way that let's them compete. For example, national entity owns the pipes and needs to provide a given service, companies compete for pipe maintenance, IT services, etc. It's hardly difficult to think up a system that is mostly free market and better in every way than what the people from the UK have to suffer through.
Railways are another example of competition not being possible and where privatisation makes no sense.
The brain is complex—adapted, or maladapted, for different tasks. My working hypothesis: mine is maladapted to the behaviors currently rewarded in corporate America. And I know I’m not Feynman.
So here I am, stuck in a bi-modal world (or maybe just worldview). This piece hits hard.