A clear vision is essential to the success of a software project. Without one, a project almost unfailingly ends up being "of two [or more] minds" about itself. Without conceptual integrity, a system threatens to become a patchwork of incompatible designs, held together by the wrong kind of screws. As Brooks states:
Conceptual integrity is the most important consideration in system design.
Stroustrup also notes:
Having a clean internal structure is essential to constructing a system that is understandable, can be extended and reorganized, and is maintainable and testable.
From which Booch summarizes:
It is only through having a clear sense of a system s architecture that it becomes possible to discover common abstractions and mechanisms. Exploiting this commonality ultimately leads to systems that are simpler, and therefore smaller and more reliable.
Compromising the architectural vision of a software system weakens and will eventually break even the most well designed systems. Having an empowered Architect who can hold the vision and enforce compliance helps ensure a very successful software project.