It is definitely not true that every successful worker is interested in further development. Many people are happy as they are and do not want to change anything about themselves. A coach would only be wasting his time with them. Even if he tried hard, they would, at most, listen to him and then immediately forget what he said.
This type of employee has already chosen a wrong path and a coach would only help him get there faster. It makes no sense to develop employees in areas you consider undesirable.
Many people feel that they are doing the wrong job in the wrong company. They believe that they should be doing something else and they are currently unable to fully utilize their skills. You can recognize these workers easily when you ask them how they would feel if the company closed suddenly. Their answer would be relief. No coach can make unhappy people happy.
A coach can't help a manager who wants to change his subordinates instead of himself. As we said, you can't help someone who does not think he has a problem. If someone only sees other people as the problem, a coach will not fix it.
-kk-