Well, I believe most of us have 10 fingers. I wonder which body parts people used to count to twelve, in medieval times. If it was their feet, it would have looked hilariously, I guess...
Most probably the reason why a 12 based system was in use in ancient times is it make it easier to divide by 3 and 4, which are in turn very useful factors in (ancient) architectural design. A decimal system was unfitted for the same purpose (divide 10 by 3 and see it cannot even be done with natural numbers).
this. it's also reflective of the proportions of the human body, which the greek architects were like mega interested in. architects use inches and feet, engineers use metric.
