Do people really do this now? Watching a movie on my phone is so suboptimal I'd only consider it if I really have no other option. Holding it up for 2 hours, being stuck with that tiny screen, brrr.
I can imagine doing it on a plane ride when I'm not really interested in the movie and am just doing it to waste some time. But when it's a movie I'm really looking forward to, I'd want to really experience it. A VR headset does help here but a mobile device doesn't.