A standard bakfiets puts the cargo lower and the rider higher, but they're rarely this wide. There are some mail bikes like you're describing, with cargo in the back. There are also bike trailers. I think this is primarily for moving plants. There are some micro trucks that can haul a pallet in the space of a bike lane.

I mean, the thing here is that the vast majority of use cases are already solved for with bikes, motorcycles, and occasionally microcars or micro trucks and the remaining cases make more sense to be centralized. Like, you go to IKEA here and you have them deliver things to your house because why wouldn't you? One truck making a bunch of deliveries is more efficient than a bunch of cars driving empty to a warehouse and picking things up. If you need to move things, it makes more sense to pay movers when you need them then to pay €10-15k (or way more, it's like $10k in the US) every year to have a car. It's just cheaper to pay movers than to own a car for moving things. There isn't really a use case for owning a car that makes sense if you have functional infrastructure.