Very simple question. Is that some kind of law or good karma? Stairs have an odd number of steps to prevent people from tripping. Most people use their right hand, so they naturally step with the right foot first. And if the top ladder is an even ladder, that person will be on his left foot. But the brain is accustomed to the right foot first, so the strange step would be to put them back on the right foot, and there was little chance someone would stumble.