In flight entertainment systems are a regulated part of the safety infrastructure onboard. A phone is unfortunately not a replacement for them, yet.
I have been on flights recently where the in-flight entertainment is delivered over in-flight wifi. I also chose to watch videos I had previously downloaded on a streaming service. Phones and tablets are already replacing these screens for some.
Many airlines have had generally available models of tablets (such as iPads) to hand out on their aircraft lacking screens. eg. Hawaiian Airlines when they still had 767s.
The issue is not that tablets can't be used, but there must be ways to communicate safety information to everyone. On planes where tablets are handed out, there will likely be alternatives for the safety aspect, and on planes with non-working in-seat entertainment those alternatives may not exist.
I've been on many planes where it was done like this - A320s I believe. Probably WestJet.
Because of the intro videos?
That and I've yet to be on a plane where the screen couldn't be dimmed all the way off via controls at my seat.
It’s not always possible, or not always obvious. I finally hung a jacket over my screen on one flight.
I always wonder if there is a product with an adhesive strip or something just for this. Like a big sticky note. Even when you manage to dim it all the way and/or turn off the screen, it seems to get reset often which is jarring and annoying