And some of them DO hold up their mobile device – possibly so they can see it and the screen at the same time. But even if they don’t, and hide it in their laps, the light shows up instantly.
You can always see an emitter much farther away than it (or someone using its radiation) can see you. This is why you can’t find things by shining a flashlight around in a field, but everyone in the neighborhood can see there’s some damnfool out in the field waving a flashlight around. It’s also why the military doesn’t always turn on sonar and radar emitters.
Except that the distractions caused by the servers are part and parcel of the Alamo experience, and people know what they are getting when they see movies at the Alamo. But just because the waiter is quietly asking me 3 times a movie if I want anything doesn’t mean that everyone else should have license to talk/text throughout.
You know, that’s probably the only downside to stadium seating. I went and saw X-Men at a cheap theater this weekend. First time I had been in a theater without stadium seating in years. I didn’t see a single person texting, although I’m sure they were.