It is not mandatory from what I know, just another way for the WBA to charge more money from the fighters. It is like other titles beside WBA, WBC, IBF, maybe even WBO. The order is: 1-3 WBA, WBC, IBF (in no order) - WBA is called now "Super" 4 WBO 5 the rest (WBA Regular, IBO, even NABO that is part of the WBO) And there are also lower titles than WBA Regular and IBO.