At least when I was a teenager 15 years ago, getting my first car meant EVERYTHING.
It meant freedom, to be able to go somewhere without parents, so after school, my friends and I could go to each others' houses, instead of just going home.
It meant we could take girls out on dates, and provided a little "private space" in case the date went well ;).
A car was also a way to express individuality. In the US especially, a car can reflect your personality and individual sense of style. My first car was an old Saab, and I filled the back of it with stickers of my favorite music groups.
A car is also an introduction to the responsibility of adulthood. In my personal case, while my parents gave me the car, I had to buy the gas for it, so I had to get a part-time job. When I got a speeding ticket, I also had to pay for it myself.
For myself, and many other Americans, a first car is like a first love.