I can't see what on earth can MS gain from making this change. What does Microsoft gain from users having a "Microsoft account"? If they go to a services model

I can't see what on earth can MS gain from making this change. What does Microsoft gain from users having a "Microsoft account"? If they go to a services model their Windows marketshare will plummet. As soon as users have to directly pay a monthly fee, all the Linux UX issues will seem meaningless.