In this case it looks more like loss aversion, protecting themselves from customer lawsuits. I'm sure there are other use cases for the data. Self-driving improvements have been mentioned.

And marketing - publicly releasing the cause of a crash when its user caused, or when the public needs to be diverted.

They're not selling it as far as I know, but you're essentially providing them with free training data for their autopilot/self-driving AI which they do/plan to make money off of. In that respect it seems odd that they would be so stingy in handing data over to the person that generated it though you can apparently purchase a connection kit to access the event recorder data for about $3k.

They offer insurance rates based on the data.