Now imagine if you had the hobby of collecting manholes? Would you hang them on a wall? Store them in a humongous scrapbook(*you'd definately get muscles from lifting it!). Trade them with friends....Hmmmmm....
Just figure there are multitudes of everyday stuff we as a race overlook on a daily basis.And never question! Kind of like the therory that 3/4 of the world looks left and right, but never up or down!