What time is it?

I decided to go to the cinema complex today and see There Will Be Blood. (Good, not great. Shouldn't win best picture, but probably will.) I looked up what time the movie started, and it started at 2:40. So I head to the theater and had planned to be there at 2:30 at the latest. I got there at 2:20. Gives me time to you the necessary room, but a soda, and get a seat in the theater. The previews and commercials start at exactly 2:40. There are 2 people in the theater besides me at this point, 2:40. Within the next 15 minutes 32 people come into the theater. Why are we all coming into the movie so late. There are many ways to look up the times that a movie starts, use the newspaper, the Internet, call the theater, they even have mobile alert text messages nowadays. I had to get up 4 times to let these late comers into their seats, plus all the people who sat down in front of me that blocked the screen. I believe that movie theaters shouldn't allow people into the theater after it starts, its not that difficult to get there on time. There was even a group of 4 people who came into the theater first at 3:10, 30 minutes after the movie started.