I could go in to the obvious; managing change, reduction and understanding risk but I won't.
Change Management is the linchpin for most ITIL framework frameworks.
For example look at Configuration Management, without Configuration Management and a Configuration Management database all processes will struggle to be embedded;
- Problems need to be raised against something, a Configuration Item for instance without a CMDB what are you raising you problems against?
- Incidents also need to have the potential to have a CI associated with it, especially in support of problem management.
- Release and Deployment, what is being released and deployed? Not in the CMDB? but it will be, if it exists.
- Change Management, hang on Change Management? Yes, ideally we want to raise a request for change against a CI.
Change Management requires Config Management? well yes eventually but you can have Change Management without Config Management but not the other way round. This is because any effort into getting a CMDB and getting it up to-date is all going to be in vain as of the first unrecorded change. How do you manage the transition of a Baseline CI through change and then released back to BAU?
The short form of this is that without Change Management the Config Management process will never be able to keep the CMDB up to-date. Any process that requires an accurate, up to-date CMDB will not be effective.
So Change Management is important.