> What if local law enforcement officer was posing undercover as an Uber customer as part of a sexual assault investigation or trying to track down all drivers in relation to a recent crime?

If they were, then I suspect that Uber would go out of their way to cooperate, using the detailed information they have on ride histories. Get a warrant, serve it to Uber, and get the data needed for the investigation.

This ignores the question of whether Uber should gather and keep that much information, but given that they do, using it seems far more useful than anything this mechanism would have thwarted.