We are creatures of habit. That's well documented. In stores, we buy a particular brand simply because that's the brand we always buy. Many of us regularly check our messages whether or not we're expecting anything because we've gotten into that habit.
And as photographers, we're inclined to photograph a familiar subject a particular way simply because that's the way we've always done it. It becomes habit and we probably don't even think about why we're setting up the shot that way.