I think because this is supposed to be FUN, not just for competition's sake. If you read the rules for the Grab Bag, for example, it says that handlers waving arms and begging their dog to do the task should be "laughed at". I'm betting that whoever dreamed this up wanted to provide a venue for the average dog lover to be able to have some fun competing and enjoying time with their dog in a
friendly environment. Not to take away from the accomplishments of OTCH dogs, but to be honest, the reason most people who don't do obedience don't do it isn't because they couldn't. It's because of the atmosphere. Not exactly welcoming, somewhat catty, and often worse. I hear people slamming each other, the dogs, the judges, etc. Not becoming, and a real turn off to newbies.