His (compelling) evidence for that assertion is that printers still jam after 40 years. For humans, writing something on a piece of paper is absolutely trivial, and if something goes wrong, grabbing a new piece of paper or a pen is also trivial. Computers _can_ now write on paper tolerably fast and well, but they absolutely can't handle even simple failure modes. And the real world is _massively_ failure-prone, in contrast to the digital domain.

Think about Tesla's pivot to "AI robots". My guess is that they'll get to something that can very slowly pick up a dropped sock and put it in the washing basket. But that it will fall over occasionally on the stairs, wrecking your kid's photos and the vase standing at the bottom, and dinging the wall. It might do a passable job of picking up the shards of pottery, but gluing the picture frames together, plastering the wall and repainting it... well maybe in in Elon's chemical dreams.