Martial artists around the world would prefer that their ranks be universally recognized and accepted, since it would bestow some worldwide creditability to their achievement, but this probably will never be the case. The martial arts were created to conduct hand-to-hand warfare; the type of warfare where each soldier has to individually fight and conquer an enemy. In war, to the victor go the spoils and the glory, so egos are important among warriors. This means that rank certification in the martial arts is ego driven and, since the martial arts were created by males, still comprised mostly of males, and are controlled by males, there is a lot of machismo. Therefore, each martial art, each martial art organization, and many times, each martial art instructor has its own rules. Similar to kids on a playground, if you want to play kickball with us, you will have to play by our rules, otherwise, go play on another playground.
So, if you want to play Taekwondo on the WTF or ITF playground, you must be certified by them and play by their rules. However, if you want to play Taekwondo on a playground down the street, you may be certified by them, play by their rules, and have just as much enjoyment and satisfaction as you would have by playing on the WTF or ITF playgrounds.
Religious beliefs are usually based upon the way people were raised to believe, or upon the beliefs of the religion to which they were first exposed. Martial artists tend to believe that the organization to which they have belonged since the beginning of their martial arts training is the best organization. They have been indoctrinated into the methods of the organization and many do not know, or have no inclination to know, about the methods other organizations. They believe that their organization is the only way to martial arts heaven.