1) there are more skiers
2) and more of them are untutored
3) and so more of them ski from the back seat
4) which results in poor timing, greater torque/stress on the body, through mis-use of the skis (as tools)
5) and therefore greater ACL vulnerability
In 1983 blew out my right ACL on 202cm pencil skis with Look RX89 turntable heel bindings.