I guess one charitable way to look at it is that after a crash, external people could get access to the car and its memory, which could potentially expose private data about the owner/driver. And besides private data, if data about the car condition was leaked to the public, it could be made to say anything depending on who presents it and how, so it's safer for the investigation if only appointed experts in the field have access to it.
This is not unlike what happens for flight data recorders after a crash. The raw data is not made public right away, if ever.
This is not unlike what happens for flight data recorders after a crash. The raw data is not made public right away, if ever.