I don't believe I am reading this kind of nonsense in HN. Or you don't know what OS is or I do live in entirely other world than you. Google or any vendor which does produce any OS'es , does spend whole year for optimizing or fixing bug in low level API. How do you feel about stagefright in you KitKat ? Or since this is your ridiculous logic, how about people still running 4.0 (let's imagine all of their "app" updates goes through google play) , what about their low level libraries , which most of the time is unfixable without major update ?
Think about stagefright , your personal data is at risk just because some stupid company doesn't give fuck about you (and me), and wants you buy more phone.
Android update issue is clash between whole hardware and software industry. remember when you buy software you was going to get update for 5year or more most of the time.
at the other hand in hardware industry when you did bought (before android) any phone, there was no update. no body cared about updates, and lets be honest the technical capability was not there in that time, so no one excepted companies to update their phone.
But regularly updating their phone require a lot of investment from companies (and at the other hand will a little decrease selling phone). which companies resist, which absoulouttly they don't have right to do.
This is fight right now between customers and hardware companies.
Specially from now on this is going to be interesting , because phones from 2015+ , is capable of doing your ordinary computation (reading mails, watching movies, etc) for maybe 7, 8 years. (just like old pc , which does run latest version of Windows 10/Ubuntu good enough right now for you browsing/chatting/watching/etc, but you cant play high end games on it).