It is a REAL ID requirement. It is federal law. States issuing REAL ID compliant identity documents must mail them to your physical address. USPS provides that data for address validation.

DPVCMRA = delivery point is a commercial mail receiving agent. Any sort of location with PO Boxes.

https://developers.usps.com/addressesv3#tag/Resources/operat...

Disclaimer: I used to work for my state's DMV.

You cannot literally use "P.O. box" but if you use the virtual street address service the USPS offers now it works just fine.

You fill out a form. The government sells the data on the form to someone who pays them money for it. There is no nuance here.

I used to work for my state's DMV. They'd sell vehicle registration data to various companies, which is how and why you get those "we've been trying to reach you about your car warranty" phone calls. I don't know about CA, but KY had a problem with tracking who ordered and who paid for that data. When I worked there, we found a number of "purchasers" who only paid for Year 1 but stopped paying afterwards.

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.

selling (data you give to the DMV) [to third parties], not selling (data you give) [to the DMV]

The DMV sells the data you give to the DMV. The DMV does not sell the data you give to the DMV to the DMV.