I love this article by Marshall Goldsmith in which he talks about why some people just don't get things done and what they need to do about it.
He says:
At the end of my sessions, I ask leaders (who have received 360-degree feedback) to follow up with their co-workers and ask for ongoing ideas about how they can continue to become more effective. A year later, about 70% do some version of this recommended follow-up (as reported by their co-workers, not by them); 30% do absolutely nothing.
He then goes on to explain why he thinks those people do nothing and what they can do to make the ecessary shift. Do read the article.