As with most martial arts (BJJ included, in the modern day) the root combat art was a complete style in its own context, IE, Ju-Jutsu contained both throwing and locking techniques. To allow the style to move forward, it had to become an ART to be accepted. Competition is the best way to grow a style. But you will lose the essence of a combat style when you attach rules to it. BJJ is going through the same kind of change now - there are the Gracies which stick to their root style and refuse to support the competition styles that are becoming popular. Again, learning advanced competition techniques in BJJ are good for the person that is competing and interested in being a high-level competition BJJ black belt. I am a believer that a teacher should have enough knowledge of the past, present and future to offer the student his choice - training, combat or competition.