So, this may be different in the UK, but in the US a large majority of travel occurs in private cars, so omnipresence of ALPRs is close to collecting data on everybody and knowing what everybody is doing at all times.
One might assume from a game-theoretical perspective that this is no different from living in a village where essentially everyone knows everyone’s business, and the knowledge that that knowledge is mutual prevents people from acting badly with the information that they have. However, in the situation where a small minority of people have knowledge about everyone else, and not vice versa, this can give that minority unearned power over everyone else.
In practice, it doesn’t feel great. I hope this answered your question.
1. Data is retained by a handful of companies. If it is leaked, you'll have a lot of information on people that is suddenly fair game for anyone including insurance companies, PI, home invaders.
2. In the US, I'm not concerned about local government as much as federal when it comes to the fourth amendment. Suppose you have a rogue potus. He sends the national guard in to Atlanta, Chicago, and Downingtown to take over the systems of these companies. Now you say, "well I'll just remove my license plate!" But these companies are cataloguing make, model, color, bumper stickers, dents; so you can take off your plate in a situation like that but they are going to still be able to track you with a high degree of certainty. People were shocked by South Korea declaring martial law -- we've become so spoiled taking these essential laws for granted. (Sorry I don't know enough about British law.)
If they don't send all license plate data to the internet there isn't an issue. But they do.
One might assume from a game-theoretical perspective that this is no different from living in a village where essentially everyone knows everyone’s business, and the knowledge that that knowledge is mutual prevents people from acting badly with the information that they have. However, in the situation where a small minority of people have knowledge about everyone else, and not vice versa, this can give that minority unearned power over everyone else.
In practice, it doesn’t feel great. I hope this answered your question.