Because Nature is Left-handed
I found this interesting answer from Wikianswers.
“We run counterclockwise because everything in nature tends towards counterclockwise motion”
The list of natural things that run counterclockwise is quite impressive. It includes: the molecule structure of amino acids, the shape of seashells, the rotational direction of all the planets (except Venus), and the orbital direction of the earth around the sun.
The list of man made events is even more interesting. Carrousels, windmills (except in Ireland), revolving doors, cable operated airplanes, the usual direction in which people spin Hula Hoops, the running track in Central park, most washer and dryer, baseball runners and Elvis’ hips all move counterclockwise.
Pretty interesting stuff!