Unless I am mistaken, this happened in Ohio. Worker's compensation insurance laws vary from State to State, so my experience with Missouri may be quite inaccurate for Ohio.
In Mo., an employer of 4 or more employees is required by law to provide coverage for work related injuries. A few of the really big employers can "self-insure", but most of us just buy a policy and pay a percentage for each class of employees wages that we pay out.
It usually costs a LOT of money each year. A few years ago, my tree workers wage rate was just short of 100% of payroll. If I payed my climber $25/hour, then I was paying the insurance company an additional $25/hr. That really cuts down on our ability to compete, so keeping injuries down is critical to profitability.
Many of the disreputable tree services just pay their employees cash, collect cash from their customers, and leave their employees completely on their own for a major incident. I knew a climber (former employee) that was nearly killed by a fall when the dead tree broke off. Working as "contract labor", he got nothing but all the hospital bills. Spleen removal, back injuries, months out of work...Not even a phone call from the scab that hired him.