In my experience, it's because most players try to lay up too closely to the hazard they are trying to avoid. I had this problem myself for a long time. I just didn't have a layup mentality, so I was always trying to get as close as possible... and as a result ended up right where I was trying to avoid. So... now I'm older and wiser... I'm a better course manager, and I almost always pick one club less than I think I need for the layup. That means that if I feel I can lay up to PW range by hitting a 6 iron, I pick one less club (7 iron) and aim to lay up to 9 iron instead... much better than hitting a PW on the next shot with a penalty stroke added.
