We are a poorer state than Georgia or North Carolina, but even with what we have, we also just invest less in coaching in general. Find a football recruiting database and look at the number of South Carolina HS recruits compared to Georgia in 2004 vs current year. That's the #1 sport at every HS in the state, and it's much worse in basketball, where girls basketball even has to fight with baseball and softball for community support in small towns.
It's an issue on the boys side too. These are top of my head, so numbers will be slightly off, but
Dorman has won 5 of the last 7 championships at the highest classification on the boys' side. They're the only program who consistently travels to top tier out-of-state tournaments and, going into the season, had lost 5 or less games against in-state competition in that time, with only one by more than a single score. In the same time, they've lost 17 (give or take) to out-of-state teams, many by double digits.
Our top girls teams do not travel and do not invest in coaching or summer development within the HS programs. The officiating is also generally terrible, which doesn't help. If you go to a top tier Atlanta program (arguably greatest concentration of girls talent rn), they view AAU/summer ball coaching as a place the girls learn bad habits that must be corrected in season. For South Carolina girls, the travel coaching is almost always a step up from the take ball and score you see in the HSL.