Some already do. Concrete, HVAC, asbestos abatement, and tree service contractors have needed coverage since 2023 regardless of employee count. All other licensed contractors must carry coverage or a verified exemption by January 1, 2028, under Senate Bill 1455.
https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202120220SB216
https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202320240SB1455