I see loads of those around my neighborhood, usually ferrying kids.

At the same time, I don't need to go 5 miles for groceries, so you might be picturing using a cargo bike in sparse suburbs. If your built environment is car centric then almost definitionally using any other mode of locomotion is going to be subpar.

IMO you don't see them in the US because they look, frankly, dorky to an American aesthetic.

We’ve moved the goalposts from “Food, beer, and cat litter would be too heavy for a bike.”

Also, my grocery stores are 0.7, 1.1, and 1.6 miles away, not that it matters. 5 miles is just not very much time at 20-28 mph. I think theft and weather/comfort are bigger obstacles to most people than distance.