We are required by law to have WC here in WI, our system works great and should be a model system for other states, from the sound of it. It's required by law, but carried by private companies.
If you are working without WC, then it seems to me you are sort of a sub-contractor. If you are a sub-contractor, you need to charge more than if you are just an employee.
A typical employee costs an employer about twice what he pays him. If he's treating you like a sub, and paying you like an employee, it sounds like you are getting screwed.
If there aren't any better jobs, pick up some private insurance, and stay safe. The reason tree service insurance is so expensive is because it's so dangerous. Some idiots don't even follow basic ANSI standards, and then wonder why they can't get insured.
If you are going to work without insurance, you might as well be your own boss.