I'll try to be clear here:

Microsoft is selling your eyeballs to advertisers: You are the product not the customer.

Vendors are buying windows from Microsoft and installing it onto a computer and selling that computer to you. You are buying a computer not windows. If you need support you talk to the vendor, not microsoft. The vendor is the customer to Microsoft, not you.

And regarding cars -- car companies make lots of crappy cars and sell them to dealerships who have to buy them regardless of if they want them or not. The dealerships are the customers of the car companies. You are a customer of the dealership. 99% of the time if you've got a problem with the car, the manufacturer is going to be of limited use to you.