The LMS exists mainly for the needs of managers...not learners.
I would say the participants in the PLENK2010 MOOC, who have decided to participate in a Moodle, would not agree. These members have all the freedom in the world to choose how they wish to conduct discussions, yet they choose an LMS. I'm willing to bet there are some who will work completely from Moodle for the entire course. So from their perspective, an LMS exists mainly for the needs of the learners.