Trending. Maintain long term data of you're driving trends, traffic along the trends, etc allows for better predictive applications.
When you look at large dataset over time people have never really looked at before, patterns emerge. Narrowing those patterns down to eliminate noise and you can use it to make better driving decisions for the individual, and society. Patterns bout your life you aren't even aware of will emerge.
Frankly, so what if someone know where you drove to last year.
Data collect and cameras are here. The fight is how it's used and by whom. Frankly, I would like the automotive companies to keep it forever but have to get my permission to give it to the government and that the government must serve ME with a warrant to get the data.