For MS, home users have been a "total cost of ownership" element in their b2b sales pitch. With home users familiar with basic MS software usage from home, MS can argue that businesses do not have to sped as much on training new employees if said businesses use MS products.
I think this is especially true today, given the reduced desktop/laptop sales in the home space, and MS's free upgrades from v7+ to win10. I think that offset was in favor of getting a smaller support base as well as the advertising channel for office365 (which annoys me, not the product, the win10 ads), same for edge browser.
What annoys me about office 365 is that yes your new Windows laptop ship with office, no you can't start using it unless you hand your personal data over to Microsoft. And apparently you have to do this within the first few months of using the laptop or else.
It's arguably a much bigger threat than home users switching since businesses could switch many thousands of machines at once