You're missing something.
The idea is to release it to APPLE customers first, because it is Apple's core (pun, har har har) market. That, and it was a way of testing the waters without going overboard and losing a bunch of money on bandwidth, data transfer, all that stuff.
So if the people they marketed it to are accepting of it, and by the data that came back they really really are accepting it, then they will branch off into the other markets - AKA Windows.
This follows the same plan as the iPod. It was usable solely by Mac users, because it was made for them to enjoy. When it caught on as well as it did, then they decided to branch off into the rest of the market - AKA Windows.