Many (too many) years ago, I routinely called "clear prop" because that is what I had been taught to do. One day, I called clear prop and was just about to press the starter and a small child appeared from in front of the nose of the aircraft
. I have no idea whether or not he had heard my call - or even understood what was about to happen - but I had not seen him approach and it drove home to me that you cannot take anything for granted, least of all that there is not someone about to walk across in front of your aircraft as you start up.
I still call "clear prop" before starting but now I do it not because I have been told to but because I know it is a valuable safety feature.
Aiglon