You have to understand how it works. When you make it mandatory, it becomes a law. That give power over to a local or federal Goverment and out of your control. You then have penalties associated with that law and it has to be enforced and abused. Making it voluntary keeps it under your control.
During my years of teaching Hunter Ed. we have seen two instances where a judge, required a person to attend one of our courses. We were not given any details as to who the person was or what crime he had commited. We only knew that they were there. I have not problem with this but it wasn't our call anyway. ....
Be Safe !!!