As a user of a 2012 Nexus tablet, I'd say it's more than that - as the OS and apps auto-update, the device feels slower and slower, with inexplicable freezes. The system alone takes half the total RAM, leading to constant swapping out of apps. I refuse to give in to the upgrade treadmill, but there's a clear pressure.
(There's also the fact that for many, the upgrade is effectively "free" with their contract.)