Guns are used to shoot. Cars are used to drive around.

I couldn’t possibly care less if the government knew exactly where and when people shoot what guns. I care that the government tracks where anyone is going at all times (because cars are required to exist in a lot of the world). The reason the government might track guns is to tell where they’re going and to ideally curb sales to criminals, whereas the reason the government might (does) track cars is straight up surveillance.