Studies have show that the more references that a borrower has, the better credit risk the borrower is. Why? There are actually several reasons, but the most obvious is collect-ability.
Why do references make my loan more collectible?
At the risk of answering a question with a question, what do you think happens when you are late for an auto loan payment? First the lender calls you. Then they start calling the friends and family that you list on your reference list. Then, when the loan is a couple months late, they start driving by your house, and your references houses looking for your/their car so they can repossess it. So the more people on your reference list, the more places they can look. An applicant with good credit can usually get away with 2 references, and only name and phone number for each reference. Poor credit lenders commonly ask for 6-10 references complete with physical address and phone number.
Another reason that people with references pay their auto loans better include that they might care more what their friends and family think about their credit. Think about it, if you KNOW that your family will be called by the lender if you are late with your payments, you would probably be more motivated to keep your payments current, right?