[wingerlang]

> I don't quite remember why

Many such system (that I've used anyway) play very low resolution movies, on bad screens, using the laggiest Android tablets you can imagine. And you have all the other things in your eyesight distracting you.

[prawn]

Not to mention that they pause constantly for in-flight announcements about duty free shopping, donating unused international currency, tray tables, dimming cabin lights, etc. That alone makes it worth bringing your own content on tablet or phone with your own headphones. If a host approaches about a meal choice, you'd see them through the headset. If there was an emergency, someone would tap you on the shoulder.