Millennials are giving up, putting off or simply choosing not to buy cars — a blow to the $10 trillion automotive industry, but a boon for people like John Zimmer.

Lyft’s 31-year-old president launched the ride-sharing service with CEO Logan Green three years ago as part of a larger service then called Zimride. Lyft is now a standalone business, letting users hail a ride with its mobile app. It employs more than 400 people and services more than 65 U.S. cities.

A significant chunk of Lyft’s growth has to do with millennial passengers, who see owning a car as less and less of a priority. In fact, from 2007 to 2011, the number of cars bought by Americans between ages 18 to 34 plummeted about 30%, according to the AAA Foundation for Traffic Safety.

“You could actually start seeing the majority of millennials in the next five years or so saying there’s no reason I should get a car,” Zimmer said. “The car used to be the symbol of American freedom. Now it’s like this, and a car is like owning a $9,000 ball and chain, because you have $9,000 in expenses on your car every year.”

That’s the secret behind why Lyft and ride-sharing rival Uber have expanded so greatly. And while Lyft trails Uber when it comes to market availability — 65-plus cities versus 300-plus — it’s obviously in rapid-growth mode, too.

Breaking down the numbers

More than 100,000 Lyft drivers give two million-plus rides a month. Lyft Line, the startup’s version of carpooling, accounts for over 50% of all Lyft rides in San Francisco and more than 30% of all Lyft rides in New York. Last year, the company saw both its revenues and number of rides climb five-fold.

That’s a far cry from 2008, when Zimmer, an analyst then at Lehman Brothers, left the fourth-largest investment bank in the U.S. just three months shy of its spectacular collapse to develop Zimride, a carpooling service originally designed to help university students share rides back home during the holidays.

“I was told by someone in the building that I was crazy to leave a sure thing like Lehman Brothers to do a crazy carpool startup,” Zimmer told Mashable.

When user adoption for Zimride proved challenging, Zimmer and Green toyed with several features. Among them: a mobile experience for booking rides that eventually became Lyft.

The startup has raised about $1 billion so far and fetches a reported $2.5 billion valuation on private markets, making it a so-called “startup unicorn” and putting it in the same billion-dollar league as Uber, Airbnb and Snapchat.

What's next for Lyft

Zimmer and Lyft plan on funneling all that cash into global expansion: Lyft reportedly is planning on spending $150 million this year alone on signing up new customers and has no plans of being profitable until 2016.

Lyft also wants to develop new product features that offer discounted fare prices and set Lyft apart from rivals.

This spring, Lyft tested out a new feature, giving a small group of Lyft Line passengers the option of waiting longer for cheaper fares. A Lyft Line ride from San Francisco to the SFO airport might cost $20, but choosing to wait another 5 to 10 minutes slashed the price by several dollars. Lyft has no immediate plans of rolling it out to all users.

"We’re still working on making it work well," said Zimmer, who added it was an experiment that may or may not be part of future iterations. “Users who saw that thought that was a really great thing to have that option. It also helps give us more time to get a better match [with riders], and therefore we can pass on more savings. But that’s where things are going to get really interesting.”

Just as interesting will be how Lyft fares against Uber. Lyft's bigger, more cutthroat rival has the added benefit of being around longer and, in turn, being in many more markets. Uber may be on a slow path to redemption, but there's no forgetting how aggressive it was in the past about recruiting drivers and customers away from competition.

So for Zimmer and Lyft, it's not just a matter of catching up, but setting itself apart in every new market it enters. Part of that will mean competing on already-low pricing and playing up their "nice guy" reputation against Uber's hard-to-shake "bad boy" image. It'll probably need more than that, though, if it wants to avoid the default fate of all nice guys: finishing last.