Given that Apple isn't worried about it's cash flow anytime soon, it makes me wonder if CD Keys are really worth the hassle.
Other vendors don't have such an expensive dongle to make money with.
... it won't help you actually understand anything about how the system works.
The vast majority of people do not want to learn how the system works. Only nerds want to do that. The vast majority of people want to use a computer and maybe they want to use it to learn something else (e.g. a spoken language), but when you make that task more complicated by having them learn how the system works, they are put off.
It seems, that some windows configurations will break this. However this is not universal, and your sweeping statement is unwarranted.
In my setup at work, there is *no* problem for me working in a windows evnironment!
Interchangeable parts won't.