There are no programs that offer such a high level of polish, usability, virtual instruments / synthesizing customization, loops, effects, and tools. Its a full featured audio creation suite, that simply doesn't have a worthy Windows counterpart.
You're right, but I would like to point out that there is much better software than GarageBad for both Windows and Mac, it's just not free.
No, I'm saying that the amount of people who need more than VLC (that is, they need to actually edit/record stuff) but who would go for the "shiny"/"easy" thing (Garage Band) instead of the feature-rich thing (Cubase) is pretty small, as well as an area that shouldn't be encouraged.
In my middle school, tons of people would go to the computer lab during lunch to play with GarageBand. The market for the "shiny" and "easy" thing is huge. Why do you think Apple is doing so well with the iPhone, that has worse hardware and less features than it's competitors.