My horse paws the entire time he eats. I can't feed him out of a feed manger as he sends his entire bed flying. I figure at 16 years of age he isn't about to stop and just cope with it. I was once told by an old cowboy it may have something to do with the natural instinct to "dig" for grass in bad weather conditions? I could be a million miles away on that theory though, I don't know how accurate it is!
Stop for a minute, open your mind, learn. You may not agree with what I say, I may not agree with what you say but we will both learn something new.