Today, many large commercial aircraft have full-fledged entertainment systems, sometimes going as far as putting a personal LED screen in every seat.
Let's just consider the costs of this for a moment:
• weight of the devices and their wiring
• power and waste heat
• cost of designing and approving the system with the FAA
There may be more I missed.
So now let's consider that today, most people (and certainly most people who can afford to fly) have a smart phone of some kind. They will most definitely bring it with them on the flight. And most people will also bring the charger and headphones (or earbuds) with them.
So you can see where this is going. If the airliner wants to provide movies or music, why not just have a jack (USB?) at every seat to plug in your smart phone and get it that way? Or possibly even provide streaming Wifi once in the air (not a true connection to the internet at large, but just as a way to distribute the movies/music). There might still be bandwidth challenges, but surely, surely this is better than a traditional IFE system as it exists today.
Am I missing something?