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.)