As a black belt I feel a tremendous sense of responsibility to the rank. I am reminded of the difference between achieving a black belt and holding a black belt.
It is said that less than one percent of martial arts participants go on to achieve a legitimate black belt. It is not that earning a black belt is physically hard, even though it is, the problem is that there is a lack of self discipline in most of us. Earning a black belt requires relentless commitment.
What constitutes a legitimate black belt? That point is something that very few will ever agree upon. Back in the day a black belt meant that you had a solid grasp of the basics of a recognized system and had your skill verified and endorsed by a master level instructor. Now you can get a black without even having a system, just a hodgepodge of techniques. There are even first degree black belts giving out black belts themselves.
Why do I bring this up yet again? Because if you cannot define a legitimate black belt, how can you define the difference between earning a black belt and holding a black belt? If less than one percent go on to earn a black belt, I would estimate that less than ten percent of those go on to hold their black belt. In order to hold your black belt, you need to continue to do everything you did to earn the black belt. I know of very few who hold a black belt in multiple styles. There are many who have earned black belts in multiple styles but holding a black belt in multiple styles - very few.
It comes down to whether the practitioner defines the black belt or if the black belt defines the practitioner. For the sake of the future of the martial arts, I would hope it is the former.