> I think the young, healthy people who live in moderate climates with good weather, short commutes, and little need to haul anything
The old dutch people riding their bakfietsen around in the snow show this is much more a cultural thing than a hard fact of weather and human nature - and culture can change as the need arises.
At everyone who can't imagine how life without a car could be possible: Watch this video! (The video linked in my parent post.) It really captures how different transportation and everyday life can be.
As a whole, reading this biking thread is an amazing example in failure to understand how a lot of small lifestyle decision lock you in a particular mode of living. I know that much of northern America is not really bike friendly. But, damn, looking at it from a German urban perspective, it does not seem like you were even trying. (And I can't blame you for that because you were missing the role models to follow.)
Half of my friends don't own a car, many of them have children. They started out by not ever having a car in the first place. We chose the cities we live in, the jobs we work for, the daycare facilities we commute our children to, all with the implicit assumption that owning a car is not desirable.
A second factor that is really underappreciated is habit. After about one and a half years of commuting to work by e-bike in various tolerable weather situations, I encountered the first really harsh road conditions. Not just snowy, but icy ground everywhere (which was definitely not fun for cars either). But because I was so used to dealing with bike challenges by then, overcoming yet another (though harder) bike challenge was so much more comfortable to me than working out the alternatives. Same with the day I was somewhat sick and there was intense, icy rain. (Nowadays I would have the decency to stay home when being sick, even though they "need" me at work).
So basically the answer to "How could biking ever work?" is "We make it work" – like with everything in life. And in the right environments, the upsides are enormous.
You are giving culture an awful lot of credit while completely omitting geography. Culture is locally adapted, and countries that are flat as literal pancakes are particularly logical places for a bike friendly culture to develop.
Parent didn't mention geography. I was mostly replying to the comment about weather, age, and cargo capacity. Obviously the difference between the Netherlands and some other flat cold place is culture, though you are right hills can impact things. One thing we can do to reduce the issue with hills is set better (higher) power limits for ebikes. The current limit in the USA of 750 watts is way too low for cargo bikes. Even for my normal ebike which I run at 1400 watts, I find it feels safer as I can keep up with the flow of traffic on city streets (though I have a lot of lighting, safety gear, and experience and I would support licensing restrictions for higher powers). The power restrictions are even worse in the UK at maximum 250 watts, which is terribly low.
The old dutch people riding their bakfietsen around in the snow show this is much more a cultural thing than a hard fact of weather and human nature - and culture can change as the need arises.
https://www.youtube.com/watch?v=rQhzEnWCgHA
As far as short commutes - that's as much a factor of public policy as are trains and other forms of public transport.