Why must I buy a life-insurance?

A vehicle was reserved by me in California with Business. The purchase price was not $9.99/ night due to a weekend package. When I examined in at the counter the agent told me that I had a need to sometimes present proof FULL-COVERAGE insurance or purchase their insurance (which may boost my daily fee from $9.99 to $40)!! They would not I want to rent a car if I didn’t do possibly then