I think it's more for show than to protect anybody.
Tech companies are selling facial recognition technology more and more each year. The government is allowed to access that information.
So cameras that incorporate Facebook facial recognition are sold to private business as a security measure. Insurance companies lower rates if you have A.I. cameras, because it makes it easier to recoup the stolen goods or criminals. The database now has a large amount of data from private companies, and the government is allowed to access that database for information.
This way the city doesn't foot the bill, people can pretend like they retained privacy (which they didn't), and business owners voluntarily provide the data. A win-win for the government. They get to track everyone with minimal cost or blowback from privacy watch dogs.