You are taught to fight until the ref stops the fight, and it is within the rules, and I am sure the UFC loves it as people like to see those type knockouts. That being said, it just goes down as another reason why the fighters need a union just like in other pro sports. It is not only for pay issues, but also issues concerning their own safety and long term well being. When a fighter is stiff out cold , it is pretty obvious, and many, if not most fighters, will stop right there. A fighter is very vulnerable and need to be protected when in that condition. But until some fighter suffers some type of serious permanent damage from those type hits , and there is some backlash that affects the UFC, nothing will be done.