Re: Rocket carcasses
SpaceX use the bottom half of their rockets multiple times. For LEO missions the top half burns up in days. The next most common mission is to geosynchronous transfer orbit: an ellipse with the low end near LEO and the high end near GEO. The payload uses its own propulsion to get to GEO and stage 2 repeatedly slows down each time it gets close to Earth and is gone in months.
As for Starman and his car: Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.