FWIW, I find it a little humorous that some of these "cargo" bikes are even given the moniker.
I'm probably a little on the "extreme" side when it comes to cargo capacity, in many people's view, but:
In many (most?) cases, any regular bike with a $20 set of side baskets on it would carry more stuff with better handling than the tiny "cargo rack" most of them have (mostly cuz the load would be lower rather than over the top of the rear wheel).
At least to me, the point of a cargo bike is to actually carry significantly large amounts of cargo, relative to the mass/size of the bike and rider--being able to replace a car for that sort of thing, at least for the most part.
Having the rack actually part of the frame can make it stiffer, but it doesn't necessarily make it a great cargo bike.
Some of the welded-on-rack types, like the Xtracycle-type racks that allow adding side carriers, etc., would be way more qualified to carry the "cargo bike" moniker than most of the others that only have a teeny little rack surface to strap to.
Of course, there are always pannier-bags that can be strapped over the existing rack, but it seems to me like having solid supports for more/heavier cargo would be more desirable for most people that need to carry serious cargo.
I've used many sorts of carrying devices, from bags to baskets to plastic buckets to metal boxes, etc., in a lot of different configurations...and I just don't see that much usefulness for a tiny rear rack like the one in that pic of the little blue 20" fat-tire bike.
Another niggle I'd put on that particular bike is that it would probably be easier to ride in the city (especially given the typical bike-lane/road-edge conditions) if the front wheel were larger, like 26" or more. I've come to the 26" front / 20" rear configuration via various evolutions of my cargo bike & trike, and it works well for not so good conditions while still having a lower-COG for the cargo area.
(someday I'd like to build up a trike with 26" frotn and rear but a deep cargo deck almost to the ground...then it'd ride even better on bad roads even without suspension).