Why does Elon Musk claim that Phd papers are useless?

I've stumbled upon this video https://youtu.be/uA_2v0d9Gzs where Elon claims that most phd papers are useless. How so? Everything we know about the universe, every scientific truth, doesn't it come out of scientific papers first? What about all the research and innovation that comes out from research centers, universities etc. that find new ways to accomplish things? Is there something I am missing here?

If it matters, I'm not a PhD student (and no interest in being one). I'm a software engineer doing my master's degree currently.