You may opt out of workers' comp for hired contractors and subcontractors. Some states fully support the exclusion, but many other states compulsorily require you to cover for anyone who works for you.
However, it is essential to note that even if you are legally excluded from purchasing workers' compensation for employees, it doesn't mean you won't be held responsible if someone gets hurt while working for you. Therefore, if you have people working under you, instruct them to get their own insurance.