@Count Adramélekh Sear
These days it’s rarely even brought up and I imagine very few people actually bother turning off / enabling airplane mode. “Back in the day” it was fairly strict; essentially the signals phones sent out
could interfere with some of the equipment. You ever hear odd beeps or boops from a speaker? That’s usually from a radio (like a police car radio) that happens to interfere with the speaker.
I imagine the tech is just better now and planes are properly shielded because they know they’ll have 50 people in the cabin playing Candy Crush while their phones scream out to the void in a panic trying to find a cell, wifi, and bluetooth signal to connect to.