A company I liked made me a job offer, which I accepted. However, they wanted me to sign a non-compete agreement banning me from working with similar companies and ALL their clients in the future. Their legal counsel said they signed the same deal with their clients by prohibiting them from hiring their existing or former employees. They had hundreds of reputable companies in their portfolio. I even sent my resume to some of them before getting the offer.
Now imagine that thousands of talented individuals with a ton of experience are limited to helping other businesses succeed, creating a cure, revolutionary technology, you name it.
They might not like the company or want to move on to another company , but those agreements limit their options.