Am I missing something? What do you mean the DMV makes tens of millions of dollars a year selling data to itself?
Federal law requires state DMVs to supply that data to the car manufacturers. So if you own a Chevy, they have to send your data to Chevy in case there is a recall.
One such platform used to be called Vigilant Systems. They'd sell details of where a car has passed a police/Flock ALPR camera, mostly to repo companies, but also bail/bounty hunters. Using details of license plate scans are more up-to-date than the DMV registration. People on the run from courts are extremely unlikely to keep their vehicle registration or driving licenses up to date.
https://www.youtube.com/watch?v=AKxkokoQdkc&t=238
The governing law is Driver's Privacy Protection Act.
https://en.wikipedia.org/wiki/Driver%27s_Privacy_Protection_...