I think the biggest reason you don't see more shifts is the lack of quality data on where the hitters will hit the ball against a specific type of pitcher. In the MLB every hit is tracked and they get 600 PA per season. Huge amounts of data are readily available. Even in college softball where the most data is available a player only gets 225 PA max in a season. With a four year career limit there just isn't enough data to be sure the shift will work. Additionally, I think egos are smaller in softball and if you put on a shift that left the whole left side of the infield open the hitters happily drop a bunt for a base hit. It pisses me off that MLB hitters won't bunt against the shift.
I have data going back years on my players, so if I were playing against them I could shift on some of them and do so quite effectively. No one else has that data, so they can't shift with any confidence.