That's end-user home enthusiast thinking and I won't argue with you for that narrow segment. But there are hundreds of millions (or billions?) of windows devices performing mundane functions in stores, businesses, manufacturing lines, hospitals, army bases, sanitation plants, etc etc. These devices don't need a trendy new UI, they need to keep working reliably and securely.
If Microsoft pulls security support in 2025, there's two outcomes and both are bad. The better but less likely choice is that these organizations squander some of their budget to needlessly turn the existing devices into e-waste in order to buy new devices to do the exact same thing. The more realistic choice is they keep running whatever app they are running, but with an insecure OS underneath that gets exploited with bad results for them + everyone downstream.
My fantasy outcome would be successive artificial breakages like this eventually lead all organizations with large non-consumer deployments to dump Windows over it. That + good success of the steam deck might finally get us free of the world's primary consumer OS having one side trying to help people and another that is actively working against them such as by artificially obsoleting their devices every few years.