Why spend the money?

I don't understand people. They spend a lot of money on things, but they don't use them to their potential. Vehicles for example:
Why would you buy a sports car, but barely even drive the speed limit?
Why would you buy a convertible - but not have the top down on a gorgeous day?
Why would you buy a truck if you don't haul stuff, drive over curbs, or take it off-roading?
There are other things that people buy and don't use to their full potential - why would you bother spending the money if you aren't going to use it??