The argument for these cameras is that they save lives. The argument against them is that they destroy freedom.
That's why these cameras are so prevalent, the case for them is extremely obvious and easy to make (give police more tools to stop bad guys), while the case against them is a lot more subtle (human freedom, government abuse, expectations of privacy, risk of data breaches, etc).
It's a good steelman/devil's advocate of their position, but I wonder if proponents realize how much wishful thinking drives those supposed outcomes.
The question isn't whether these cameras help law enforcement. Of course they do. The question is whether that's sufficient justification for continuous government surveillance of the public movements of millions of law abiding citizens.