The reason we have a drought of good pitchers is because...
....pitching is hard work.
also, I think since so many girls start at 8U and 10U, they are developed by parents/coaches who are after short-term success.
"Just throw strikes!"
Attend any 8U/10U game and you'll hear it.
For every successful D1 pitcher, there are 25 girls who could mow 'em down in 8U, 10U , 12U;
and then started to hit a wall at 14U and were done playing on top competitive travel teams by 16U,
if not earlier.