If Microsoft want to tie you down to their store then they ought to giveaway the operating system for free, considering how they intend to profit from you buying from their store and from the all the sneaky ways they collect information about you.
They want to capitalize off your personal data, provide you "apps and ads", so why should I pay for that from the start. (I would install on custom PC).
If you're giving it away free then it's like I'm agreeing to the apps and ads as long as I'm a user of the OS.