Why Stack Exchange for Android is using ActionBarSherlock, this makes app bigger and slower. The ActionBarSherlock adds action bar support to older android versions (Android 2.x), but Stack Exchange for Android requires Android 4.x! What is the reason?
This (ActionBarSherlock) allows you to easily develop an application with an action bar for every version of Android from 2.x and up.
The ActionBar APIs were first added in Android 3.0 (API level 11) but they are also available in the Support Library for compatibility with Android 2.1 (API level 7) and above.
Android Support Library + ActionBarSherlock increases the size of the application of 600kB+