It depends on the state. But generally sub contractors carry their own insurance.
In NYC when a GC hires a subcontractor, the GC is listed on the Subcontractor’s Workman’s Comp Insurance as a certificate holder. The property owner is usually listed on the GC’s policy. It could be different in other states. Anyone could verify this information by visiting their workman’s comp website.
We make sure that all subs we use have up to date Ins before we let them on any job. We list home owner as additional insured and have subs Ins Cert available to home owner if requested
In Louisiana, most GC require subcontractors to carry their own insurance policies. GC are normally added as a certificate holder or additional Insured.