Don't know why you're being downvoted. Musk has consistently said their main goal is to become the most advanced manufacturer in the world. Building the machine that builds the machine is what they're aiming for.

Probably because Tesla hasn't had much success in terms of advancement of automated assembly. They went down the same rabbit hole that a few other automakers already explored and discovered what others already did—that high levels of factory automation simply doesn't work. (Yet.)

At best, Tesla factories are currently comparable to the state of the art in terms of car factory automation.

You obviously don't follow Tesla very closely. Sandy Munro of Munro associates has literally called Tesla's engineering "mind blowing" and at least 5 years ahead of any other manufacturer. If you are not familiar, Sandy Munro is one of the leading automotive manufacturing experts, if not the top expert. So I'm going to take his word for it rather than yours.

YOU obviously don't follow Tesla very closely. When the great grandparent said "Tesla's revolution is a more automated assembly", they were flat wrong which is something Elon himself admitted. Tesla tried to go big on automated assembly and failed.

https://twitter.com/elonmusk/status/984882630947753984

I have watched most all of Sandy's videos; they are orthogonal to assembly automation. The exceptionally impressive things Tesla have done in later revisions of the Model 3/Y (particularly the octovalve and the rear body castings) are related to advanced manufacturing methods which reduce part counts. Not factory automation.

Sandy is very good at styling himself as a premier industry expert—and he's quite likely one of the greatest automotive manufacturing experts on YouTube. But I don't think most serious automotive manufacturing experts are spending much time posting on YouTube...