You're so right. A few years ago, I went to see Of Mice and Men with my girlfriend in the West End of London. The cinema was nearly empty. I said to my girlfriend something along the lines of I bet the next person who comes in sits in my way. Then a woman came in and sat almost next to me. When I whispered about this to my girlfriend, she got up, went round the front of the seats, and sat almost next to her! Jerks.
One other thing, please remember that some people actually watch the titles at the end of the film. So if you're a person who isn't, please get lost quickly and quietly from the cinema before you start talking loudly or putting your coat on with a maximum of flamboyance. Mind you, as with the movie Dodgeball, you can very easily miss something great.