Wow MMach5, thanks, I never knew the reason for it.

I often find myself using hand signals at the 4-way stop on my ride home... I turn left, there is almost always traffic in the direction I'm going and the opposite direction, and sometimes from the right, almost never from the left. But usually what happens is the drivers going the opposite direction don't feel like waiting and I have to gesture to them to stop when it's my turn to go.