Before we get too off-track... CMMI is meant to help engineering development organizations improve on their capability to consistently and predictably deliver the products their customers want, when they want them and at a price they're willing to pay. From a purely inwardly-facing perspective, CMMI helps companies get from estimates to actuals in the black.
Without some insight into and control over their internal business processes, how else can a company know how well they're doing before it's too late to do anything about it? And if/when they wait until the end of a project to see how close/far they were to their promises/expectations, without some idea of what their processes are and how they work, how else could a company ever make whatever changes or improvements they'd want/need to make in order to do better next time.
CMMI provides the models from which to pursue these sorts of insights and activities for improvement. It's a place to start, not a final destination. CMMI can't tell an organization what is or isn't important to them. CMMI, however, can provide a path for an organization to achieve its performance goals.