Change is hard because people don’t only think on the surface level. Deep down people have mental maps of reality — embedded sets of assumptions, narratives and terms that organize thinking.
David Brooks
What struck me about Brooks' statement was the idea of 'mental maps' and 'terms that organize thinking'. Certainly there's no challenge to the idea of 'change is hard' -- this is accepted routinely and said often. But as a root cause, I'd never really thought of the organized thought thing.
Asking (or imposing on) someone to reorganize their mental map of values and beliefs is no small matter. As a matter of professional necessity, many are able to separate their personal map from the new/changed/different map given to them by their job/profession/organization/project -- but many are not, and they are left deeply conflicted and unhappy (perhaps, unproductive as well) ... or they leave.
Sometimes worse than re-mapping, change may trigger fear losing what we've got. To wit: it was too hard to get here to lose it now. (See: Prospect theory)
And, unfortunately fear is always an easy sell, possibly even layering on some elements of paranoia, but always driving resistance and defensive actions.
In short, change is hard!