Punishment has been demonstrated to be a completely ineffective and counterproductive "teaching" tool. Negative and Neutral Rep are just ways for people to attack one another without violating Forum rules.
Edit: Rather than repeat myself, here is what I said bout Neutral Rep previously.
No one has ever been corrected by negative rep. The mere suggestion is honestly sorta entertaining. People may have been spurred on to change how they do things based on feedback from the community, but that can be provided via many other, far more constructive ways. PMs are a great way to deal with such matters.