My family uses our cargo bikes as our primary mode of transportation year round. It turns out that children were allowed to leave the house prior to the invention of cars and continue to be capable of wearing jackets in the winter. Many even like the snow.

The key thing to understand is that while sometimes you need more than a bike can carry, that's a small fraction of all of the vehicle trips Americans make. The average trip we take has 1.2 people in the car, is a relatively short (half of them are under 3 miles, a distance my son could do on his own as a 2 year old), and carries negligible cargo. Buying a vehicle for your 99th percentile needs is a significant expense for capacity you use only a handful of times a year — the average American spends $11k/year to own a car according to AAA, and for that much money you could buy and discard a new cargo bike every couple of months and still have plenty left over to rent a truck on the few occasions when you need landscaping or building supplies.