Aquila
Retired Moderator
Actually it is related to Android because it is "open" so therefore Google does not have control of its own OS in terms of both features and software updates. Nexus phones are not big sellers and Google has never been in the customer service/support business for Android or their services so you are kind of on your own when you buy one. Now they have made a great move to be able to update their services and apps without OEM and carrier approval but again it leaves them powerless when it comes to their OS and features added by OEMs.
To a point that's somewhat correct, but the manufactures don't have any desire of their own to update your device. They sell it with whatever version it's on and expect that'll be good enough for most consumers. If you buy a device with 4.1 on it and want one with 5.0, they'd really rather you buy their device that ships with 5.0 on it.