Plans fail in many business organizations for the these reasons:
Lack if seriousness and commitment to a plan by the planner.
Failure to use strategies and tactics that are sound and consistent with the objectives and policies of the organization.
Lack of adequate techniques and information for monitoring performances and controlling the plan.
Failure to delegate commensurate authority to those responsible for implementing the plan.
Making decisions alone without involving interested particular, thereby killing relevant initiatives and support.
Failure to attend to detail and to consider all the essential aspects of a plan. For example, failure to identity all the possible internal and external threats and to make provision to deal with them one after the other