If I'm checking messages / emails / whatnots while watching a movie or tv program, the movie or program has failed.
Okay, I accept this premise. Most programs have failed. They are not sufficient to be the sole focus of my attention for an hour or two. But you know, sometimes they're good enough to have on in the background while I'm doing something else that's *also* not sufficient to be the sole focus of my attention. I can listen to an audio program while I work on chores or crafts. I can watch TV and mostly ignore the video. Or I can watch 3D TV and mostly ignore the video. But if I'm going to mostly ignore the video anyway I'd rather mostly ignore 2D video where I can just glance up to see the interesting bits, rather than mostly ignore 3D video where I have to find special glasses, put them on, and rewind to catch an interesting bit that's already gone by.