I seem to remember that someone decided, after running the numbers, it seems that Microsoft makes a loss from Windows over time. But it's considered to be a useful loss leader for that MS Office which is very profitable. The move to the subscription model, makes this somewhat moot. It was Office 365, now its Microsoft 365, and you will have Teams forcibly installed and you will use it!
Hence, I think the real reason for the change will be to limit any liability claims for holdouts when Microsoft stop providing updates to all users.