Why hasn't the under hand freethrow shot ever caught on?

I read a story where...obviously Rick Berry touted it as far more accurate...I forgot the reasons but it's so much softer of a shot so you can miss but if you hit the rim not atrociously - it can bounce in.

But he said...(paraphrasing) that it's an additional skill you have to learn apart from normal shooting and players are:

1) Lazy
2) Think it's going to mess with their shot

lets say shaq learned how to shoot underhand and hit 75% vs his career 52.7% (rick barry's was 90% or so)

He'd move from 28596 points to 31100 points roughly 300 points less than wilt