I'll add another one, borne painfully of recent experience: projects are often delayed because people aren't interested/capable of providing meaningful input on

I'll add another one, borne painfully of recent experience: projects are often delayed because people aren't interested/capable of providing meaningful input on things until the critical moment is imminent, and that's usually late in a project, and then you have a pile-up of critical moments yielding real input. Moreso in bigger organizations where you have very little influence on the participation and quality of input by cross-domain team members.