The fact that there are over 3 billion android users in the world is really mindboggling when you weigh that against the fact that there are 4.66 billion people who have access to the internet. The average netizen owns one or more android devices. This alone makes android development very attractive to both developers and tech companies.
CONSUMER'S PERCEPTION OF THE SMARTPHONE MARKET
There are however things that people complain about when it comes to smartphones, things like how mobile phone manufacturers are using planned obsolescence to force people to buy new mobile devices, a sharp contrast to the good old days when our phone could fall from the second floor without needing to be replaced or repaired. While some of the accusations aimed at smartphone makers are true, I want to share some insight into the process of developing android applications which in a way affects android smartphone makers because they don't own the android software, anyone who wants to make phones with android operating system needs the permission of Google (who own android) and must agree to comply with Google's terms.
A LITTLE HISTORY OF ANDROID PROGRAMMING LANGUAGES
Now let's start from the bottom, Android operating system (OS) is written mostly in Java programming language, however, Kotlin (another programming language) is said to be a new replacement for Java as Kotlin is easier to use than Java but makes uses of a lot of Java programming language resources. Java as a programming language is owned and managed by Oracle, Oracle recently announced that people who use Java programming language to build products will have to start paying for it, it didn't go down well with most of the tech community as we're used to making use of programming languages for free. Now Kotlin is owned and managed by JetBrains (another company) and seems to be providing an alternative, don't worry I'm still going to tie everything back to why smartphone makers try to sell you a new device yearly.
THE ANDROID VALUE CHAIN
The way things work is that the people who manage programming languages are constantly improving on the language to make it better and faster (because all programming languages compete against one another) as the most productive languages get used more and can relegate others. As programming languages evolve they more or less require the android operating system (which is built on said programming language) to also evolve as new features and capabilities become possible. As the android operating system evolves they tend to require that smartphone devices be built to set specifications in order to support the new bells and whistles of the android operating system.
THE MAJOR DILEMMA IN ANDROID DEVELOPMENT
Android developers also have to choose whether to build using the latest update of the programming language which will work with the latest Android OS (and have all the shiny new features but won't support most devices) or to build with older programming OS in mind but lacking all the new features. Some organizations are comfortable enough to build for all OS and some have to decide their priorities, only 10.4% of android users have Android Pie (9.0) OS running on their phone while 90% of android users can run applications built for Android Jellybean 4.0. For companies that have cash constraint, they may just focus on building applications that can run on Android 4.0.
These are some of the dynamics at play in the smartphone industry, it's also why the industry isn't in a decline, everyone gets paid at the end of the day because smartphone makers (by making phones with the latest software) help drive demand for better software solutions. It won't be financially possible to continue to pay developers to extends the utility of programming languages that reflects on the operating system.