California construction workers least insured of all groups

Why is this happening in the most heavily regulated and taxed state in the nation?

California Construction workers have the lowest level of medical insurance of any other non-farm labor group in the state. Some 27 percent are chronically uninsured and 40 percent uninsured during part of the year. Only 35 percent receive health insurance through their employers. As much as it rankles many, a national health care policy would alleviate a most of this.