Excuse this question new to Android world. (Iphone dummy). But why is ir up to the carrier to decide when to up grade? Again in iPhone world, the whole eco system ( newer phones) get the update
Posted via the Android Central App
Unlike Apple, which controls iOS with an iron grip, Android is an open source platform. That means that each manufacturer can modify it to work however they want on their specific hardware (which is sometimes good, sometimes bad), and the carriers can then put their own tweaks/modifications/crapware on the software after the given phone manufacturer finishes their tweaks. Apple doesn't really let the carriers screw around with iOS. It comes directly from them to the phones.
Also, since Apple's the only one who manufactures the iPhones, when the update to iOS comes out, any iPhone/iPad capable of running the update is able to get it right away. Again, Android usually needs some tweaking to make features work on specific phones (such as added stylus functionality for the Note 4).