If you ride in a town or city a lot, you know one big piece of the answer: jealousy.

If there are more cyclists, you’ll see them more often riding by you at red lights and lines of cars at stop signs. Drivers hate this; it reminds them that sometimes cars are slow, and they love their cars, so they get angry.

If there are more cyclists, drivers will have to be careful not to hit them, and being careful is annoying. Right now, depending where you live, the driver can say “almost no cyclists are out here, so I wasn’t expecting them, they need to be more careful”. And the drivers believe it, and their friends do, too. But more cyclists around would make those excuses look like the BS they actually are.

And related to the second point is that, if cyclists increase in number, they will demand (and get) more bike lanes and protected areas to ride and park. This will absolutely come at drivers’ expenses. Drivers know this. So even though fewer cars would decrease congestion, drivers know that they would be inconvenienced in other ways, and that would again remind them that they aren’t as important as they want to be.

Finally, in the US specifically, large SUVs and trucks are causing massive increases in dead pedestrians, children, and cyclists. The increased death rate over the last ten years is appallingly high. If cycling is normalized even more, clearly political opinion will shift, and those giant vehicles will be heavily restricted or taxed, or their insurance rates will skyrocket, or drivers will be charged more frequently with manslaughter for the death that they cause every day. People are reasonably afraid that their unreasonably large vehicles will be taken away from them.