A single newborn can be handled without a car (if you spend used car prices on a stroller system!) - but if you have three kids under three, or five under 7, a car greatly simplifies things - or you need to hire additional wranglers.
It's not about the good times (on a good day, moving five kids by walking/stroller is easy) - it's about the bad times, the crying, the screaming, the attempted suicides, etc.
Until you're the only adult in the car, driving along the motorway, and one of the kids in the back starts crying / gets car sick / needs the toilet when you're 15km from the next services. Granted, train toilets with a toddler aren't much fun either.
Don't need a crazy expensive stroller though. A sling when they're small and light, and once they get big and heavy, they're large enough to go in a more basic foldable stroller. The childcare products industry is honestly awful at scamming new or expecting parents into buying shit they don't need.
Singles - I agree. Even doubles, there are reasonable ones.
Find a good cheap triple or higher stroller. Then you're looking at used car prices.
And I agree - a train is nice with a family, because once you're in, you're in.
But a train is more like a plane than a car; it's the subway that's closest to short commuting trips, and they rarely have bathrooms and often subway stops don't have them, either.
(Sometimes the temptation to get an RV with a toilet is high, mind you.)