"Once upon a time there was a language called J2ME", you will not be surprise if you hear this few years later. But it should not be forgotten that each of these languages have its own context or domain which can vary according to the needs of the customer.
Why & Where...
A well known truth about J2ME is that it is a sandbox language. I.e. It always needs to stand on top of a another language stack (OS) & hence J2ME is always restricted to access some kernel level functionalities of limited devices because of this 3rd party behavior. For instances one can not write an app which can be auto-started in device boot up without using some other party interaction like push registry. Of course by using push registry one can write an app which will auto-start but via a timer, sms or http like interaction signaled by an outsider. Therefore without any interaction auto-start in boot up is impossible in J2ME. Another scenario is accessing device key pad for locking and unlocking purposes is also impossible as J2ME is not allowed to access locking API of the device. Actually J2ME does not even has such an API for locking. One more thing to notice is that every mobile device has a settings programme which is responsible for managing installed applications. In J2ME context you can never write an app to get the control of this settings app which is silently handled as a device kernel level programme.
As mentioned the primery reason for this is J2ME is a third party language pre-configured and installed on top of another core language stack of the device. For example simply consider Nokia mobile phone which claims to support for J2ME. But the fact is Nokia has its own language stack as the core of the device called Symbian. Symbian OS has its own rich APIs to directly interact with hardware level and other core functionalities of the device. Symbians S40, S60, Symbain 3 are examples for such Symbian OS APIs equipped with SDKs to leverage developers for developing apps. Both the carbide.C++ and the later added framework called QT C++ can be used for writing applications for Symbian OS. Above mentioned impossible scenarios in J2ME can be achieved via these two implementation frameworks.
But as J2ME hides internal complexities from developer, for developing some typical enterprise level apps, J2ME is apparently efficient and easier than using Carbide or QT. Hence language depends on requirements as always. Focusing on Android here is irrelevant because it is that big buzz word everybody talks about these days. To be it as this much of huge buzz, its complete OS stack has played an incredible role. Because of this perfect organization from ground level APIs to higher level APIs in its OS stack, developers have been able to develop apps without considering dependencies, hardware abstractions, library couplings etc. But there is an one little problem with Android. I.e. its fast growing development life cycle. Not like any other OS versions of other devices, Android does not provide long term service for once released version. They tend to grow fast and if earlier version can not tolerate with the later version, bad luck for the users those who have that earlier version of device. But generally people rarely open their mouths up on this.
Therefore Why and Where is a decision made by developers.