Part of the problem with facial recognition is it is potentially inaccurate, especially if you are not a white male.

So you run the risk of having large numbers of innocent people being incorrectly tagged as persona non grata - be that with the police, in-store detectives, hotels, potential employers etc.

Having a computer say "this person is bad/unwelcome/a shoplifter/bad credit/a sex offender/etc" is powerful, and difficult for laymen to counteract. Computer says no - sorry, it's policy, nothing I can do.

And you can do this at huge scale for pennies and in the blink of an eye with a computer. You can't do that with a human manually/semi-manually doing it.