It's not as bleak as that. There are a lot of people with manufacturer-abandoned phones that would probably be willing to shell out a modest sum to get less ancient firmware. As with everything, the economics are a question of quantity and effort. A billion Android devices enter the marketplace each year.

I think the real problem is that it is just turning out to be difficult to make a silky smooth upgrade process, the kind that is consumer-friendly enough to create a mass market. It all fundamentally starts with "hack the device" and most people can't. Maybe it's just a really hard problem because it varies from device to device and base OS version to base OS version.