Better in-flight seat back systems and BYOD systems both seem to be happening. I'm not sure if there is a difference in philosophy with different airlines or if anecdotally-observed different approaches are just a matter of timing.

I could imagine airlines preferring systems, such as the one United is pushing these days, of customers using their own tablets/phones for reasons of cost/weight. It also gets customers onto their app and perhaps increases the rate of purchased WiFi.

On the other hand, seat back systems can run ads etc. and are often a premium service. They're also just convenient for a lot of travelers who may not have a charged and loaded device for everyone in the party.