> What's to stop them from selling this license plate data to the police or to other parties to pad their quarterly numbers?

Motorola does!

https://drndata.com/

If you're a private repo-man you too can also buy Vigilant Solutions (now Motorola) ALPR cameras to track down deadbeats and take their cars.

Note the list of "Trusted by Fortune 500 data-driven companies" there. All of them are sub-prime lenders and cater to the 24.99% APR marketplace.

Even funnier they now sell the bodycams over through DRN too to the repo guys. https://drndata.com/body-worn-camera/