Re: "It looks like users won't adopt it if they have to pay for it"
Win10 runs on a phone, a small tablet etc. even a Pi, sort of.
No need for a new PC, therefore smaller sales.
MS need to sell it for 19.99 Home, 29.99 Pro and make sales happen to existing users, not too many of which care a great deal about the slurp that occupies so much time here but might want the latest OS to 'make it all work better'.
The masses are really not able to just run Linux (Mint or otherwise) totally themselves; most don't have friends who will set them up and many would not want to be reliant on someone else. Most don't know of the options of course.
It would be interesting to see a truly large effort to tell people that there is a solid, reliable, alternative to Windows that doesn't cost the earth like an Apple device and promise to support it and help with issues and get traction with Program developers etc.
Say, sell Mint with support for a year for 19.99, on the assumption that the system will be solid and reliable and thus not too may will need support anyway.
This sounds like a good business opportunity, the 20 quid is free money since the product supplied is free.
If it gives no trouble at all, it is basically a license to print money; hard to believe it is not happening at scale anywhere.