This is not a trivial matter. Students devote much of their lives to their martial arts, masters, schools, and organizations. Some organizations and masters only think about themselves and their business and will forget all you have done for them when they do not need you anymore. It is not a good feeling to be rejected by those you have looked up to and given of so much of your time to make them successful.
As I write about in TKDTutor, rank certification not governed by any local, state, or federal agency so it is virtually meaningless anywhere other than inside the organization that issues it. Some organizations recognize rank certifications of other organizations; some do not. This makes it difficult for a person to leave an organization or school and join another one without having to work up through the ranks again. When you train with an organization or instructor that does not issue any type of certification, this makes it even more difficult.