Where to stand

When waiting for my partners to play I have always tended to stand behind them either just to the right or left.  This I find the best position to sight their shot and advise them where it has gone if they lose it in flight.  If I stand to the side and have to move my head to follow the ball I quite often lose it. No one I have played with has ever has ever complained about me standing behind them. 

However the etiquette section of the rules of golf states, "Players should not stand close to or directly behind the ball when a player is about to play." Can anyone explain why this is considered a problem.  Is it because they might catch sight of you in the backswing although I can't see how if they are looking at the ball or is it a safety issue if the club slips out of their hands in the back swing? Or am I misunderstanding what the etiquette section says?

So if I'm standing 4 or 5 metres back and a metre or two to the right or left I'm OK.

Thanks Chris

I am not that fussed where they stand just as long as they keep still, as any slight movement will be picked up in the peripheral vision.

Safest place with me is directly in front!

I believe, Mat, you have to be 3 paces either side of the line of your opponents put, but once they have played the shot you can move to directly behind to watch the line, sneaky monkey 

I play with one person who stands directly behind me on all shots which was really annoying & often put me off. I didin't want to make a big deal out of it so I used it to my advantage & started to ask him if I was lined up OK, where my feet where pointing etc.

When this started to help me he stopped standing behind me!!!

J.