Statis:
The High School League sets a minimum number of schools that must field a team in a sport in order to make a classification in that sport "go". I am unsure of the exact numbers, but 1A and 2A boys used to be combined until enough 1A schools had soccer teams. At that point, 1A boys was able to split off. I believe that was about 8 years ago. It is not about the strength of the bracket, it is about fairness, logistics and legitimacy. If was all about fairness, the SCHSL would adopt the promotion/relegation system that has been discussed on this board in years past.
Currently 1A girls is short of the required number... thus 1A/2A girls is still combined.