Since the release of Kit Kat, where Google are turning off previously available features.
If your device has user-accessible internal flash storage, your SD Card is a �secondary external storage device�.
What this means is that with KitKat, applications will no longer be able create, modify, or remove files and folders on your external SD card. As a for-instance, you can no longer use a file manager to copy files from your computer to the SD card over a network. This ability, which has existed since the beginning of Android, has been taken away.
Samsung Galaxy S4, Note 3 Android 4.4 Problem hits Micro SD Card