[mabbo]

And that works well if you have a small number of SKUs with a set weight and dimensions. Amazon has billions of SKUs.

The robotics and ML needed to be able to open a storage bin, see what items are inside, choose the one you are looking for- and only it- and then carefully pull it out without disturbing the other items, that is the problem Amazon faces with full automation.

You could reduce the number of SKUs per bin, but then you have a storage problem- there's way more SKUs than bins in a building. You could go slower, but then you have a throughput problem.

It's really, really hard. And while humans have a high opex, they're really good at that particular problem. Hands and eyes are incredible tools. Robotics is catching up though, and it's awesome, but it's not there yet.

Source: I spent many years working in Amazon Fulfillment Tech (and these opinions are my own and do not represent me speaking for the company).