Why are people sheep?

A couple of my favorite, "people are sheep" examples:

1. You're leaving the movie theater and there's two doors. One door is open, so everyone is squeezing through that one and creating a bootleneck. Why does no one ever bother to check the second door? Invariably it's unlocked.

Are people assuming people AREN'T stupid?! Of course your fellow lemming movie goers haven't checked the other door. They're dolts.

2. Today, Thanksgiving holiday travel. I'm in the American Airlines line at Louisville Airport. There are three self-service check-in's. Is anyone using them? No, of course not. They're all standing in-line waiting behind the proverbial "one door" line. I ask, from my position eight people back, something to the effect of either "those are open" or "is anyone going to use those" and one lady moves forward; after that standstill.

We get a little closer - I'm exasperated at this point - so I move to the head of the line. A woman calls out, "I'm waiting for those." Naturally there's two open and some dumbass dad who's never been on a plane before is blocking one of them. Sending his rotten kids back to the wife/mother; another broken home!