It’s hard to believe, as New York’s Citi Bike celebrates its fifth birthday this month, that it was once considered a radical idea. In September 2017—the city’s most popular month for biking—New York City’s bike-share system served up more than 70,000 rides on eight separate days, and over 60,000 rides on ten more. In total, Citi Bike allowed for more than 4.3 million gas-free miles traveled around New York that month.

That’s a big achievement for a brand-new public transit system. (And yes, municipal bike-shares are a public transit system.) For context, Miami’s 25-mile, 23-station Metrorail averaged 68,400 riders on weekdays in October 2017. To take an example closer to home, New York City’s Economic Development Corporation projected that average daily ridership on its six-line ferry system would be slightly more than 12,000 per day. (Of course, Citi Bike has lower numbers in the winter—but even during a bitterly cold January, it averaged more than 23,000 riders a day.)

The program’s success is part of a larger two-wheel trend. Chinese cities today are thronged with cheap, pay-per-ride bikes that may have permanently changed urban travel patterns there. Santa Monica has a new billion-dollar startup providing electric scooters to grown-ups. And Uber recently spent a reported $200 million on the electric bicycle-sharing startup Jump.

But even recently, this future was not so clear. Thursday is the five-year anniversary of a memorably apocalyptic video testimonial by Wall Street Journal editorial board member Dorothy Rabinowitz called “Death by Bicycle.” In a follow-up, Rabinowitz decried the influence of the “all-powerful bike lobby.” But that goofery was far from anomalous. Gothamist has rounded up some of the fearful predictions that accompanied the rollout of New York’s shareable blue bicycles:

• New York City will get sued.

• Citi Bikes will ruin historic neighborhoods.

• Citi Bikes will “severely endanger the health and safety of the residents of 99 Bank Street.”

• “The bike-share program, however innocent its intent, represents another governmental incursion into the private marketplace.

• Rather than encourage business to develop creative solutions to gridlock, the government has imposed its own solution.”

• Terrorists will use Citi Bikes to carry bombs.

• Michael Bloomberg is like the Taliban.

That all feels very distant now. While Paris’ Velib and Washington, D.C.’s Capital Bikeshare came first, no system outside of China rivals Citi Bike for ridership. The system has more than demonstrated that bicycles are a legitimate, widely accessible solution to short-distance transportation in a congested city. (The average trip hovers a little over 2 miles, or about 40 Manhattan north-south blocks.) It has given hundreds of thousands of people the opportunity to try riding in the city and, by making bicycles a regular part of the urban streetscape, changed the way drivers behave.

And yet: In many ways, the system’s success remains chronically underappreciated in its own backyard. New York City Mayor Bill de Blasio has slowed his predecessor’s commitment to creating new car-free spaces, letting two of the city’s landmark greenways—along the Hudson River and over the Brooklyn Bridge—languish under record traffic. This will be the first year that Citi Bike won’t expand, despite a desperate need for new transit options in Bushwick (which will lose its direct subway service to Manhattan next year) and a total absence of bike-sharing in the Bronx.

The system’s success remains chronically underappreciated in its own backyard.

According to Streetsblog, Citi Bike parent company Motivate was close to an agreement to expand the network by 50 percent, including in a big area of the Bronx, but the deal fell through because de Blasio was reluctant to sacrifice parking spaces.

Instead, outer-borough neighborhoods will get trials of dockless bikes that cannot be ridden into Manhattan. (Citi Bike has an anti-competitive clause in its contract.)

Most perplexing of all, though, is the city’s continued reluctance to provide public money to support the system. Rare is the New York transportation option that does not obtain some subsidy: Private cars depend on hundreds of miles of free parking; Ubers, Lyfts, and taxis on free access to midtown streets; subways, buses, and trains on public funding.

Thus far, Citi Bike has made do setting up its docks in a handful of repurposed parking spaces and extra sidewalk real estate. Beyond that, it obtains no meaningful public subsidy at all. At $169 a year, an annual membership is still a bargain. But you have to wonder: Why hasn’t the nation’s most successful transit startup drawn in any public funding? And what could it do if it did?

There’s evidence that localized sponsorships can boost ridership in low-income communities of color. In Brooklyn, for example, a grant-funded collaboration between Citi Bike and the Bedford Stuyvesant Restoration Corporation boosted membership at a rate 10 percentage points higher than in the city as a whole. Enrollment by public housing residents grew faster in Bed-Stuy than anywhere else in New York. Trips in the neighborhood shot up by 70 percent from September 2015 to 2016. The work, the BSRC reported, “is changing the face of who rides in Bedford Stuyvesant, encouraging more people to use Citi Bike for commutes and pleasure, and giving long-time residents new ownership over changing streets and new safety infrastructure.”

Having profitable transit should never be a city’s goal. To the extent they increase ridership (beyond a certain point, they may not), transit subsidies are investments that reduce the externalities of auto traffic, including accidents, air pollution, lost time, noise, road deterioration, and greenhouse gases. So if you have a transit system—like Citi Bike—operating with no subsidy, you are probably looking at a massive missed opportunity to expand its user base.

It’s not as if the de Blasio administration is philosophically opposed to the concept of public support for transit: The mayor recently announced another $300 million in capital spending on a ferry network that also draws in $30 million of public money for an annual operating subsidy. To translate that into bike-share economics, the annual ferry subsidy would pay for almost 200,000 annual Citi Bike memberships.