Overcoming process inertia is profoundly expensive and often demoralizing to teams. The project budget for a new system is often pitched as vendor price plus some internal oversight, but this fails to represent the cost of the project exactly because adapting the workflow of a whole division or organization inevitavly costs some multiple of that budget while vendors, consultants, and internal spearheaders all pretend it's negligible.

You're right, ultimately, that failure to adapt is the final damning issue in many of these projects but the root cause of the failure is often that nobody sincerely quantified just how costly and disruptive it will be.