For Windows, Firefox/Chrome, Java, Flash critical updates are issued each couple weeks, and as far my understanding goes, it is REALLY bad not to install them ASAP. For my 3 year old Samsung smartphone, however, there isn't a single OS update. A brief research shows that in most cases you can't upgrade your Android version for most phones in a year or so after release. Given that smartphone in many cases is a very juicy target for hackers, with all two-factor authenthications, email and bank passwords going through smartphone, it sounds very scary that there are basically no updates for OS/firmware.
Is it really scary? If yes, why don't google enforce stricter policy for manufacturers, or don't make OS update by itself? What is situation with iPhones?