Besides courtesy, also helps for safety.
I will usually use "FFFOOOUUUULLL
BAALLL", in the hope of spending less time explaining that it's the ball's position and not the fielder's position.
Besides, that's what I was taught.
Also, that you always call a foul, but point fair (never verbal) only when it's close, deflected foul, or you think your partner needs a signal.