Twice yearly roll out of incompatabilities
Now that Microsoft has got a large number of machines being upgraded when it wants it can start to roll out code that breaks other systems; be they those who are still running old versions of Microsoft Windows (ie not 10) or those who run non Microsoft operating systems or applications. Eg Linux or LibreOffice. They roll out applications that handle a new file or wire protocol in March and then make it default in September, removing use of old protocols next March, so software more than 1 year old will then not interoperate with the latest stuff.
They will claim that this is all in the name of progress or fixing security vulnerabilities; but the real reason will that they will start saying how non Microsoft software is incompatible, not good enough, ... So LibreOffice (and similar) developers will have to waste a lot of time playing catch up while Microsoft sniggers.
Other software vendors play this game, eg Autocad is continually updating file formats which makes it hard for users of old versions to read files from a user of the latest versions.
This will also help with forcing people to take out a subscription: no subscription so you don't get the latest Microsoft Word ...