There's another completely different reason for the use of paper vs. electronic stuff and it has to do with certification.
The power available charts in the FM are in the 'approved' section of the FM - checked by the certification agency and approved as being accurate.
The electronic one is not checked - this is a whole ball of wax (or is it worms) that the certification agencies don't want to get too deeply into. How good is the software in the electronic system? Is it certified to DO-178 Level whatever? How do you check to make sure it is valid in all conditions, etc.
Real problem in the fixed wing world for takeoff performance, etc. You can use electronic stuff all you want, but you still need to verify it with the old paper - until very recently, this was the case.
I understand the FAA has now allowed electronic data, but with some sort of approval process. Wheels in this area turn very slowly.