Realistically, there really isn't much of a danger for using mobile phones and other electronics on planes. One can find headsets for use in general aviation aircraft with Bluetooth, so that the person wearing the headset can use their phone to make calls, or to listen to music, or whatever. I even had my flight instructor call his girlfriend while I was landing the plane. I would send my girlfriend pre-prepared texts at certain points in the flight so she wouldn't freak out.

The FAA can approve certain devices to be used throughout a flight (example). Approvals like this, however, are restricted to specific devices, on specific aircraft (with specific avionic suites) for specific operators. It would become logistically difficult for the FAA to try to test all of the permutations of devices, avionics, airline interior trims, and aircraft to certify that there isn't any danger. This doesn't even take into account the possibility of an individual altering the hardware inside one of these devices either for nefarious or benign purposes. So, while there is a very, very, very small chance of something happening, it is non-zero, and that is too large for the FAA to change their regulations.