Same with holding up ten fingers. We don't have to count to ten. We know its ten

Well, I'm not so sure, Wordwind. I can prove you have 11 fingers.

Please hold up your left hand palm facing you, fingers outstretched.

Start counting backwards from 10 starting with your left thumb.

10 - 9 - 8 - 7 - 6 + five more on your right hand = 11.

Now, think how confusing it would be if you had your left hand in your pocket and you held up your right hand, palm facing someone in front of you, and they started counting down from your right pinky.