Currently most just go inside hierarchical workplaces where they have to learn to play office politics and carry out meaningless job functions in exchange for financial security.
We don't have a Bell labs anymore, science is getting more expensive and most of the venture capital money goes to software rather than to the more capital-intensive lab equipment plus salaries.
We as a society train all these phds that then leave their field of expertise because there's no opportunities. You can try your luck as an underpaid postdoc and hope that you get an amazing article on a high reputation journal and at the same time a faculty position has opened up (because the faculty died) for the particular niche field you are an expert in. That's a lot that's utterly outside of your control. So most just go into finance/consulting/tech and move on. All that training, for nothing.