Left Hand Turn....

Tell me why, please for the love of Pete, do people hesitate on a protected left hand turn light? This could possibly be the number one thing that gets me cussing, as well as golf, bowling, putting things together...but by far possibly the worst. I mena, I don't get it, you know that you are in a turning lane, protected by a left turn only signal...why, oh why, do you then wait 5-10 seconds before you go? This is really annoying when the light itself last no longer than 15 seconds.....UGHHHHH!!!!