I think one of the differences is speed, so there is a huge difference between riding at 5 to 10 MPH than driving at 50 MPH.
Now, E-Cargo bikes, of course, bring in a mid speed of 20 MPH or so, perhaps even faster if given a very hot motor.
Tires also give a fair amount of spring.
There has been a discussion about springs in the Clydesdale subforum. At least many off the shelf spring systems aren't designed for 300 to 400 bikes/riders.
As a cyclist, I'm also pretty good at avoiding bumps (in part due to experience with pinch flats).
Anyway, I'm not sure if the springs are necessary. Perhaps if one is moving to a 3-wheel trike giving a lateral component to the bounces which could affect control.
Of course, there are springs in seatposts, handlebars, and etc. Perhaps easier to configure the springs to a rider, rather than compensate of a dynamic load of 0 to 500 lbs or so.
And, of course, weight. Even for for cargo, adding extra weight to the system may not be desirable.
Here were some photos of a cargo bike meet someone posted earlier, some bikes with suspension.
https://www.bikeforums.net/utility-c...-nijmegen.html
Anyway, in the future, we'll likely see a mix of some bikes and trikes with suspension, some without.