I had the privilege recently to spend an hour in an LH A380 flight simulator in FRA and was instructed by their most senior check captain. He clearly mentioned that technically there is no reason to prohibit use of phones. There is no impact whatsoever to the aircraft.

However, the reason airlines have the no phones policy is so that pax are not distracted in case of an emergency evacuation. That is the only reason. Some airlines are more strict than others (with BA,LH the policy is phones off if the doors are closed, whereas e.g. AA, CX the phones can be used after landing once the plane is off the runway).