Learning from experience

As a long-time advocate of retrospectives, one of the most rewarding parts of the teacher training course was seeing the idea of "learning from experience" in a different context. A large part of the art of teaching is actually about encouraging learning: moving beyond the transmission of knowledge and practical skills so that pupils develop their own "metacognitive ability", identifying the ways in which they learn and reflecting on their own thought processes in the light of experience. (Happily trainee teachers are also expected to do the same and become Reflective Practitioners through a mixture of self-evaluation and mentoring).
Learning to Learn seems to be a fairly hot topic in educational research, and in my reading around it I often found successful learners described in terms such as "resilient", "resourceful", and "reflective" (definitely attributes I have seen in the most successful software teams, and the individuals within them). It was extremely rewarding as well to read Papert's book "The Children's Machine", whose emphasis on how we learn through exploration – reaching conclusions about abstract concepts through progressive, concrete experience – resonated with so much of the debate in software circles about emergent design.
Back in the business world, people like Senge have been popularising the idea of learning organisations for a long time. So why do software teams, even Agile ones, often see (or gain) so little value from retrospectives? Are the retrospectives not being done "right"? Do teams see the retrospective event as the only time to reflect so that they miss the learning opportunities that crop up more frequently? Or are there so many limits to what people are "allowed" to question and change within their organisation that they simply give up on the whole idea of trying to learn and improve...?