There was a day and a time when these rules made sense. It was not that long ago that consumer electronics use to give off a ton of EM interference. I use to have an old Nokia brick phone that gave off enough interference that you could hear it connecting to the cell towers on any nearby amplifier within 30 feet.
But that was over 10 years ago. Modern equipment no longer uses analogue transmission for anything. Everything is digital, on very specific frequencies, and at much lower power than they use to be.
Even if all 100 people were all streaming netflix and making phone calls at the same time, then so what? That is like saying that you cannot see what is in front of you because the IR or UV rays of the sun are too bright. Other than possible physical damage, the amount of it hitting your eyes will have no affect on what you see because your eyes are incapable of seeing those frequencies. Similarly, airlines are not using the same frequencies, or communication protocolls, as what consumer equipment is using. The argument is like saying that you cannot hear what someone is saying because there is a bright light in another room. Or that you are having trouble "smelling the color 9" because "colorless green is sleeping furiously". It is just nonsense that has nothing to do with eachother! Even if the same bandwidth was used the sheer amplitude at which towers and planes can communicate should be more than capable of shouting down the other electronics.
Or put another way; If airlines are using equipment that is so easily interfered with by consumer electronics then the FAA and FCC should be held responsible for making and implementing standards so that this is not a problem. There is always going to be a prick that leaves their devices on out of spite, or someone so jetlagged and clueless that they forget. So lets make sure that standards are set so that this is a non-issue.
However, I do understand the need to at least put down devices (and books) during the safety speech for liability reasons, as well as the need to stow all items upon decent because in a crash a cell phone (or anything really) is just a large bullet and could kill someone who would have otherwise survived. Those are legit reasons, but outside of that then it should be free reign.