Pointing or hammering a swinging strike is for the benefit of someone who might have looked down or away when the pitch came. This keeps these folks from asking "hey, what was that pitch" when they weren't paying attention. It also makes it easy for the official scorer, who is busy writing and may not be able to tell if it was a swing or not.
Compare it to a Ball call. If the pitch goes way over the catcher's glove all the way to the backstop, do you really need to holler "Ball!" at the top of your lungs? Of course not. In fact, you don't even need to say "Ball" at all, because by definition it is a pitch which is not called a strike. You need to acknowledge "Strike" calls, but you don't need to say "Ball" if you don't want to (though most umpires do). The same goes for obvious "Safe" calls. No signal needed, except on close plays. A physical "Out" signal should be made on all outs recorded at any base, close or not. If it isn't close, and the runner is safe by a large margin, no "Safe" signal is necessary, since if the runner is not out, the only other choice is safe, and it is obvious to all that he's safe.
Now, you should be more confused than ever!
