Do you say the auto dealership has free gas because new cars come with a full tank? Apple sells MacOS for money just not à la carte.

Given the upgrade cycle for computers, they are making substantially less (and OEM gets a massive discount over the store shelf price of windows).

Since they arent getting a massive markup on very well integrated, mediocre hardware, they need to sell more than just Windows. Office, SharePoint, etc are where the real money is at for them.