I don't see why an app stored on an SD card cant be RUN in internal memory, which after all is a temporary status.
Secondly even if this is the reason there have always been some apps where it was marked impossible to move to SD so that takes care of apps that need internal memory.
There will still be a lot of apps that do not need to hog space on the internal memory.
Actually since it is often stored data (like large music collections in Spotify) why isn't it possible to set the data to be stored on external SD. In the same way how can I force apps like my devices camera to save files to the external SD. OK I know I can move them there afterwards but it would be so much easier if I could set the storage location in the first place (if this can be done please describe the process) What about other folders such as downloads etc.
It strikes me that Android needs something similar to the excellent Windows libraries that are in 7 and 8.
I am still firmly of the opinion that the reason Google have dropped this support for moving apps to SD, is to increase the sale value of devices with larger internal memories - costing many times the value of the space on a micro sd. Interesting that this came about as Google moved itself into the hardware market!