I actually was one of those developers, for a number of years. The reality is that we're still very far away from a robot that can visually identify random objects, identify them, and then pick them up in a safe manner. Humans are awesome at exactly that.
The automation is coming, yes, and many very tedious tasks are being automated but Amazon has never laid off warehouse employees because a robot replaced them- they just move those humans to jobs robots can't do yet, and grow faster.