The concern is that if the government is tracking where you go while you're inside the car, they also have a pretty good idea of your actual destination, which

The concern is that if the government is tracking where you go while you're inside the car, they also have a pretty good idea of your actual destination, which could be a problem in e.g. states with laws against abortions even in other states or if, say, a school teacher was tracked to a known gay nightclub in Florida.