The left lane is reserved for passing and faster moving vehicles. It's amazing how backed-up traffic can get from one inconsiderate driver. Please just move over.
Moderator's Note: You are right; the law tells us to stay right, except to pass. The law also tells us to drive no faster than the speed limit, even in the left lane. If we all observed the speed limit and stayed right except to pass, we could expect fewer traffic back-ups ... and fewer traffic accidents.