Also, most users aren't really aware what's using up the resources - only that their computer gets slower with time. I actually wish Windows would start naming & shaming applications - e.g. by showing a balloon when the system slows down, that would say that application X and Y are consuming most of the resources.

As it is now, CPU, RAM and storage usage are perfect externalities for developers. The result of their abuse is user frustration, and reduction of the number of things people can do on their computers. That, and wasting user time. Unfortunately, there's no way that would make the developers suffer costs for wasting user's resources, so the only thing that lets us have lean software is engineering competence and human decency (both of which seem to be in short supply).