Any Jiu Jitsu practitioner who has been training in the style for a relatively decent amount of time will know that getting their black belt is something that needs to be worked on for years and years. It is not something that can just happen overnight. Hard work and dedication to their martial arts is one of the most important ingredients that any practitioners should have. Black belts are something that need to be handled responsibly, and they are never given to children, no matter how good the child might be. However, in addition to the belt itself, there are many people who simply do not want to proceed further after their blue belts.
One of the reasons that people believe that many practitioners stop at their blue belt is the fact that they hit a difficult plateau with their training. It is something that always happens to a lot of people, at just about every belt level. There is a period of time where the practitioner simply sees no improvement in their skills. Many can get frustrated and quit after this, not understanding that it is just something else that must be improved. While it is something that happens to white belts more than blue belts, the attention to the higher level results from people not understanding what the blue belt is. Almost all black belts have the same advice for blue belts, and that is to keep going and training at their best.
Check out the Gracie Breakdown