1. Groceries
In your first semester, you will learn that campus foods get old quickly. Being able to drive to get food is essential, but people are not always willing to drive, and if they are it gets old asking every couple of weeks.
2. Going home
It's very hard to coordinate with the people back home to see who can pick you up and drive you home. It would be much easier to have your own car.
3. Money/environmental benefits
It would be more efficient on overall gas consumption to have your own car. Two roundtrips would take WAY more gas than one. So getting your own car would be better for the environment in that aspect.
Note: Show this to your parents as a persuasive tool.