It's not about the fee (generally it's small for you (though for the OEM it's critical, and one of the ways MSFT gets OEMs to do their bidding (a small example is how they all "recommend Windows" on their sites; it's a discount on the fees they pay MSFT)). The fee also is why you get so much crapware on new Windows boxes.

It's about the hardware's support of the OS (see the firmware discussion above).

It's also about your support experience as a customer (do you have to reinstall Windows before the OEM will give you the time of day, let alone fix the hardware glitch you're hitting)