One reason for using statins though total cholesterol can be even below the lower limit is that the ratio of hdl to ldl cholesterol can be out of whack. Supposedly, they are supposed to increase your hdl to balance out the ldl. For example, my hdl was 12 and ldl was 117 for a total of 129. My doctor put me on a statin to increase my hdl.
The problem with that is my liver enzymes are a little high all the time now, and I'm on HRT currently 200mg/2 weeks although I used to be on 200mg/week. My doctor tried to blame the high liver enzymes on the HRT, but I wouldn't let him since I know that statins can mess with your liver. I never really had trouble with my liver until I started on the cholesterol meds.