Yeah, and Linux will probably have an even longer support period. But MS is in a totally different business. HW manufacturers build and sell new devices to customers who then buy software from a different company (MS). One of the selling point of Windows is that it runs on basically all HW. But they can only afford this because they have monopolized the market.

The mobile phone business is very different. (But you may argue that that's the problem.) The HW manufacturers sell the SW bundled with the HW. As soon as they have sold the HW, the software is just a liability (while for MS it's a recurrent revenue!). Not only that, but the longer and the better the SW works, the less likely you are to buy new HW from them. (And since that's the only thing they are selling, it means the less likely they will see a revenue from you.) Now this may imply that the business model is flawed and maybe it will change as the market matures and people will stop buying newer and newer phones every year. Just like it happened to desktops and then laptops. (I'm typing this on a 7+ year old Thinkpad and the only thing I miss is +16GB RAM.)