I'm not sure why people keep coming back to the idea of martial arts ranking being in any way like professional qualifications. They are different in very important ways.
The AMA has a monopoly on the qualification process for doctors of allopathic medicine in the US. This process is open, rigorous, and competitive. You take a competitively graded exam to get into an accredited medical school, pass a competitive admissions process, then take and must pass many courses taught separately by independent instructors and also graded with competitive exams before you receive a MD degree.
In fact, the AMA does *not* have a monopoly on the qualifications/licensing of physicians in the U.S. That was decided by the U.S. District Court Judge Susan Getzendanner, who stated that a the AMA had engaged in a "lengthy, systematic, successful and unlawful boycott" designed to reliminate the profession of chiropractic as a competitor in the U.S. health care system.
Of course, the AMA failed, because people have demanded an alternative to one-pill-fits-all medicine, and chiropractic physicians such as myself are working overtime to meet the demand.
In the same way, aikido has developed many branches, because it serves many needs.