Driving pet peeve

When driving from my brother-in-law to my in-laws house, I say something that always seem to tick me off. When there is a lot of traffic, why do you think you can get out of line, try to pass 2 or 3 cars, and then squeeze right back in, causing everyone you just passed to slam on the brakes behind you?

While I am on it, why does everyone rubberneck in South Carolina?