If they don't have to deal with cars, perhaps it's ok - but yikes. Helmets for everyone because even at 20kph someone could get a nasty/fatal head injury when they're yeeted out of the cargo area.

Try to count the number of helmets you can spot:

https://www.youtube.com/watch?v=pqQSwQLDIK8

https://www.youtube.com/watch?v=ynwMN3Z9Og8

In Amsterdam if we see adult cyclists with a helmet we'd guess it's probably a tourist or new expat. For children most parents only bother with helmets until they're six years or so.

The cargo area in mine has seatbelts sized for small children.

"Why I stopped wearing a bike helmet" by former editor-in-chief of Bicycling, the world’s largest cycling magazine - https://www.cyclingtips.com/2018/11/commentary-why-i-stopped...

(Although he does still say kids should wear them).

It's all in a combination of infrastructure and riding style. If you're forced to ride with car traffic you have to go fast, which predisposes you to an aggressive road biking style. But if you do that then you also have trouble with stops and starts, which creates additional risk.

If you can go slower like a Dutch commuter, then you can also ride like them, using a step-through frame and a lower saddle. That keeps your center of gravity down and allows scooting starts. All of this adds up to a substantially smaller risk of going head-first in a fall.