I am amazed by the Bakfiets, but i am confused at why delivery guys aren't already using it, there must be some reason for why these are unusable in other count

I am amazed by the Bakfiets, but i am confused at why delivery guys aren't already using it, there must be some reason for why these are unusable in other countries, like, here in italy we see delivery guys everyday and i think that if someone found it useful they would've already started using it, so, why not? What is keeping people from using the Bakfiets? There MUST be a reason for this.