Some developers don't allow you to transfer their apps or games from internal storage to SD card. For example: Whatsapp.
This might be a reason!
anon(238680) and Laura Knotek like this.
And the reason they don't is that the app won't work if it's moved to the card, so they avoid having to handle all those "the app doesn't work" complaints from people who moved them.
For you apps that use lots of data space (camera, GPS, maps, games, etc.) check the settings in each app to see if they allow their data to be stored on the SD card while leaving the app on the internal storage.

