What’s the difference between dealing with a car insurance company directly or a local agent?

I was with the same insurance company for 10 years using the same local agent. My car insurance rates kept going up every time my policy was renewed. I decided to explore and see what better rates I could get with other car insurance companies. Friends and family gave me names of local agents from insurance companies they used. All the agents quoted me really high. Then, I called a major insurance company’s 800 number (not through an agent) and got the lowest quote. So, why do people use insurance agents? Is there a reason why it’s better to use an agent?