[AlotOfReading]

The data isn't open because it's not required to be. Every manufacturer is either making a good faith effort to collect that data (to their own standards) or they probably shouldn't be on the road. Regulators, NHTSA especially, don't have the expertise, time, or mandate to get it from them, analyze it, and make it available. That could (and should) change though.

As an unrelated aside, measuring safety performance is hard. Doing it accurately without putting vehicles on the street is probably impossible. Simulation is not a fully adequate replacement for road testing and many companies are already looking at cutting the latter because of the expense. It'd be nice for regulators to outline an acceptable road test framework that better balances the goal of public safety from unsafe vehicles against ensuring safety can be demonstrated in real world environments.