Listen, I don't care if you've been doing yoga since you were a fetus, because even if you are physically capable of scratching your ears with your foot, you would never do it in public. Talk about inappropriate. Hey everyone, my ear itches, so I was thinking you could all check out my crotch while I sit on the floor and scratch it in a very compromising position. On top of that (which is a place I wouldn't recommend literally getting on top of, just figuratively) it's impractical. Why not just use your hand? It's so much easier, and doesn't put your hamstrings at risk.
But none of this is true when it comes to dogs and cats, because as far as they're concerned, there couldn't be an easier and more polite way to get rid of that ear itch.
(flickr photo Those darn ears by Jimmy 74(away); http://www.flickr.com/photos/jimmy74/2576145832/)