Of course there are multiple rationales for choosing a platform, but support is certainly one of them. A while ago someone made a nice graph of how good Apple/Google are at maintaining OS support for their devices, it's pretty informative (although I'd like to see a new one). http://www.fidlee.com/android-support-vs-ios-support/ In this case the Nexus 4 is still officially supported by 5.0... but not being able to ca…
However that being said: That graph really makes the entire ecosystem look dysfunctional. All smartphones should have full support for at least two years regardless of manufacturer and the fact most don't is a poor reflection of everyone involved.
Android needs a Linux style package system. They bundle too much stuff together into singular giant update packages, when in reality you should be able to update e.g. Dialer, Browser, and so on without touching the Linux kernel or Android services.