I think you forgot the parts where even devices with a 3 year old OS [1] regularly get updates of many APIs that have been (sensibly) decoupled from the OS, have access to substantial compatibility libraries and so on.
[1] By which I mean Froyo, Gingerbread doesn't hit its third birthday until December (at the earliest).
[1] By which I mean Froyo, Gingerbread doesn't hit its third birthday until December (at the earliest).