Cannot install or move Android Apps to SD Card - is it a flaw from the Android or from the phone manufacturer? From my understanding, while the Galaxy S4 does offer a memory card slot, it's worth mentioning that you can't install apps on the memory card and can only use it for storing movies, music, pictures, etc.

So, is this a problem with the Android 4 OS not capable of allowing phone user to install or move apps to the SD card?

or 

is it that the phone manufacturer are not capable of producing a phone that allow user to use the SD card slot given that the limited space for a 16 GB Samsung Galaxy S4?
Android supports moving apps to the SD card since version 2.2 (only for apps which allow it); however, this feature can be disabled when building the ROM. Apparently Samsung decided that about 9 GB of user-accessible internal memory should be enough for apps, and disabled the “move to SD” function in their stock ROMs for the 16 GB Galaxy S4 model.

However, there are recent news that Samsung heard complaints of 16 GB Galaxy S4 users and enabled the “move to SD” function in a software update.