When writing apps for Android and iOS it is important to keep in mind the different versions of each system. You want to use new cool features that are available in later versions but you do not want to alienate too many users by using features that are not compatible with their phones.
The Android documentation recommends developers to ensure that the app is compatible with at least 90% of active devices. For Android this currently means that the app must support all versions going back to Ice Cream Sandwich (version 4.0.x). This is the fifth latest release including Kitkat (version 4.4)
|4.0.3 -4.0.4||Ice Cream Sandwich||15||7.8%|
Meanwhile, when developing for iOS targeting iOS 7 means that 96% of users can run your app as of today. This also means that iOS developers can focus on a more modern UI and not having to create separate look-and-feel to cater for very different operating systems. Android 4.0.3 was released in October 2011 while iOS 7 was released almost two years later in September 2013.