Many traditional auto lenders only work with dealerships. If you're buying from a neighbor or off Facebook Marketplace, a personal loan gives you the cash in hand to close the deal fast.
For most, a standard auto loan is cheaper. However, a personal loan is the better "story" in these specific scenarios: can i use a personal loan to buy a car
Banks often refuse auto loans for cars over 10 years old or with 100k+ miles. A personal loan has no such restrictions on the vehicle's age or condition. Many traditional auto lenders only work with dealerships