An employer in California is free to ask questions that help determine whether the prospective employee is honest and law abiding. If your state requires driver's to have proof of auto insurance, compliance with that law would tend to show respect for the law and/or honesty. If your driver's license is suspended due to reckless conduct or alcohol abuse, your employer would find that information helpful in determining whether to trust you as an employ with access to company property and resources. So long as the request for information is not discriminatory or otherwise violative of state or federal law, the employer can ask. Of course, since private employment is voluntary, you can refuse and find other employment.