I flew on Emirates a few months ago and not only did they indeed have seat-back screens, they also had a really nice selection of movies. Lots of choices, including a number of 'sets' like the entire Star Wars series, the entire LOTR collection, etc. Nothing can really make a 14 hour flight good, but I was pretty satisfied with the quality of the hardware and content on the Emirates plane.

Where do you fly?

All the Australian, Asian, ME, and Canadian flights I've been on in the past 5 years have had them except for porter air which is short haul flights from Toronto. Really just US airlines I've seen this happening in but they were always pretty barebones.

Out of curiosity are you primarily flying short haul flights in US / Canada? (I know Air Canada rouge has ditched a lot of screens.)

Im genuinely curious because almost all flights I've been on have screens in the seats.

I recently flew on Air Canada and Polish LOT, and they both had functioning screens and movies... maybe it's just your airline or region?