One word: insurance. Rates for drivers under 25 are upwards of $200/mo in most urban areas, and that's for the utmost basic 'one-way coverage' insurance. Under one-way, if you are deemed even partially at fault in an accident, however minor, the insurance pays the other's bill only - and essentially ensures you cannot drive for the next three years as premiums quite literally skyrocket. Anecdote from my university ye…
I used to live in Toronto, bought my first car when I was 20, got into an accident at 21; I couldn't afford insurance and hence a car again until I moved to the US at 23. It isn't the same here, my wife and I now pay $200 every 6 months which is 3rd party and liability (the one-way you mention) and convers both of us. Also 1 accident in every 3 years is forgiven. (I live in California)