National health insurance regulators and consumer advocacy groups tracking consumer grievances note that large-scale legacy insurers frequently record the highest absolute volume of consumer complaints, primarily due to their massive market share and millions of active policyholders. Common grievances filed against major health insurance providers typically involve disputed claim denials, delays in prior authorizations, surprise out-of-network billing disputes, and frustrations with customer service navigation. Smaller or regional insurers often report fewer total complaints simply due to lower enrollment volumes, though customer satisfaction scores can fluctuate widely across different state jurisdictions.