I believe the following 9-points are why leaders & managers don't implement plans.

Look forward to your comments?

1. Lack of motivation: The journey is not do-able because there is no compelling vision, no obvious reward, and no fuel or spark for persistent action.  Followers will say, “Life is already too busy to tend to a lukewarm plan.”  
2. Decision rights, information flow, and lack of responsibility: key people do not know which actions and decisions they are responsible for.
3. Strategy, planning and implementation are separate projects:  Coming up with a plan is the easy part, implementing it requires the right attitude.
4. Unrealistic reliance on past qualifications:  “While the doctor reflects the patient dies.” Italian Proverb
5. Lack of skills or ability to accomplish tasks:  Just plain lack of experience & training.
6. Politics and teamwork:  Alone in an organisation, it is nearly impossible to be successful without the support of other individuals.  
7. Sub-standard research capabilities:  Managers often relegate the researching of the “what” and “how” to subordinates.
8. Misconceptions of corporate position:  The executive has no idea how important it is to lead by example.  Somehow, they feel, and hope, that everyone else will lead and manage the organisation.
9. The comfort zone:  Why risk failure by sticking their neck out?