This hits cars harder: both because almost all of us will reach a point where we can’t drive safely and because cars are one of the leading causes of poor health both due to the hundreds of thousands of severe injuries caused annually, significant air pollution, and the negative health impacts of sitting immobile and training their users that any exposure to the weather or walk longer than a driveway is to be avoided.

Weirdly the good health needed for biking is procured easily by biking.

It must be nice to stay 25 forever.

Bicyclists do tend to stay in much better shape than drivers, it’s true, but I’m reminded that I know more adults who can’t drive safely than bike and several of them were in good health prior to being in some kind of car crash. The status quo in the US is 40k deaths due to driving and hundreds of thousands of life-altering injuries every year so there’s considerable room for improvement here.

That is not universally true. Health conditions aside age has a big impact here on everything from distance to duration, frequency and speed.