As a kid, we used to go to the movie theater armed with a squirt gun, and thought it was the height of hilarity to shoot our friends and watch them try to figure out why it was raining. As a grown-up, it's not as funny, primarily because the local theater closed and now we're stuck going to a mall multi-complex, where most of the audience are strangers.
Actually, most folks are pretty courteous at the theater we frequent. It's probably social pressure - behavior is contagious, and we're lucky enough to live in an area where people are generally thoughtful of others. That's not to say we don't have our share of oblivious/inconsiderate asswipes, but they're in the minority.
Gads, does that mean we have a politically correct social program coming for the idiots who fail to recognize social niceties?