When your in a brand new aircraft then I agree with the statement regarding cbs are not switches, but in the real world of old jetboxes with batteries and turbines that have seen better days, conserving battery power is essential. I also think it comes from the training and students sitting in the aircraft running down the battery for 20 minuets before hitting the start button, so instructors would pull the cbs and therefor the newbie pilots would continue to do this for ever more...but that's just my opinion for what it's worth.