I think every time I speak/write about the learner, I mention motivation at least once. As an ID, I take motivation very seriously. It is my responsibility to ensure that the learner's motivation is high as this will ensure that he/she actually learns. We do a detailed contextual inquiry to understand our learners. Then, we brainstorm for hours before we decide on the instructional strategy that we should use.
But regardless of the effort we put in, if the internal motivation is low, it is a tough situation. The learner should want to learn. I see this in my daily life whether it is working on a project, writing a blog, conducting research, working on a presentation... If the motivation is low, it shows. We may try to encourage them, push them, force them but none of this will work if their heart is not in it.
What influences internal motivation? Internal motivation is influenced by one's aspirations, goals, and needs. We have to understand these to ensure that their heart is in it. If we understand this, we may be able to show the learner the relevance and arouse their curiosity. But, if they still don't want to, they will not learn. That's scary... We can only ensure that we play all our cards right and hope that the learner is inspired enough. The onus is finally with the learner. I guess this goes back to the basic principle of adult learning: What is in it for me? We can show this relevance but it is for them to see it.
Please note that I am not trying to pass on the blame for courses that have not met their learning outcomes. I am only reflecting on the power of internal motivation.