Why do so many soccer players tear their acl?

Nature of the sport. The nature of soccer requires twisting and pivoting on your legs, which puts your ACL at risk for tearing. Females are tearing their ACL's in soccer at a 3 -5 times rate, compared to males.
Pivoting. The soccer player probably performs the most cutting motions per athlete per game. Each time a player plants the foot and turns to the outside, the acl stops the knee from rotating and converts that energy. There are many thoughts about the actual mechanisms, but soccer players perform the offending motions over and over again. Some studies have shown limited benefits from plyometrics training.