Why Do People Use Harsh Bits?

In the right hands (professional hands) bits like those can be useful training tools. Unfortunately, most of the people who use them do not have the right hands. I think it is kind of a control/fear thing that drives people to use them. They a) want ot have full control over their horse or b) are terrified of losing control. In reality, they just end up hardening the horse's mouth and causing them a lot of unneccessary pain.