Car culture, as another poster said, is a rite-of-passage in the US.

When you turn 8 years old or so, you typically get your first bicycle. And this lets you exert some independence from your parents - you're able to ride faster than they can run and catch you for the first time. Later, you might get a better bike and be able to ride even faster and further. You can spend an entire day away from home on the weekends, visiting friends that you'd otherwise have to ask mom for a ride to go see.

But the downside to a bicycle is that when it rains, you're probably going to be stuck wherever you are. And then you turn 16 and get your learner's permit. Now you're able to go faster and farther, and travel when it's raining.

So it's part of the process of the little bird leaving the nest and becoming an independent person.