Curveballs and Little Leaguers

I recently came across this quote about youth pitchers and curveballs.

"The unnatural contortions of the arm and elbow are harmful enough to the pros, to say nothing of young athletes whose bones and joints are still growing. We shouldn't put pressure on them that will ruin the development of their skeletal structures and lead to deformities."

Speaker: Robert Kerlan, Sandy Koufax's orthopedic surgeon.

Spoken: 1976.

Admittedly, I am fixated on this issue. But it is incredible to me that Little League Baseball - and other youth leagues - continue to resist rules banning curves. The notion that the clinical evidence isn't there is laughable. How much evidence did Little League need before requiring batting helmets?