And then what. Nothing gets done to the thief. The photo goes into some database, where it's never looked at again.
Those license plate cameras capture a picture of who is driving each stolen car.
And then what.
Like I said before, its not a silver bullet. But it is a resource. Investigators could drill down in the most important cases, like where there has been a murder. Repeat offenders could be identified and flagged for apprehension upon reentry. The Intelligence Community could scour for patterns to map out cartel operations.
Just because they don’t grab every petty thief, does not mean its useless. They might even let the petty criminals go, to preserve the capability to catch more important prey, like terrorists and drug smugglers.