You're right, but it's not common in America, that's where we come in, with a few other tricks and tech up our sleeves...
I agree that there is a lot to improve upon the existing designs. Don't worry, my surprise was not meant as criticism on your project.
So then why are you surprised?
This isn't a normal thing in North America and seems like you are a fan of the service, so the funding is justified. Maybe it's an obvious concept but it's not developed here.
Normally technology is invented in Silicon Valley Start-Ups and then either copied or expanded to Germany. To see a slow developing company like the German post company (previously government owned) use a technology for years and then seeing people getting totally excited about the idea in the US years after is just a strange experience.
It's a normal service of the US Postal Service too, but they will only allow mail in the box; FedEx and UPS are not allowed to use them.