Interesting article, however I think the main problem is the premise that all, or even the majority, of graduating PhD students wish to continue to work in academia.
It will be different across industries, but I work in a pharma R&D company of around 120 people. At a guess, around 40% of the entire staff (admin, management, scientists, technicians) are PhD graduates. They're working in industry and reasonably well paid.
The point is that a desire to secure senior academic positions, such as tenured professor, are not the only reasons people decide to pursue a PhD.
It will be different across industries, but I work in a pharma R&D company of around 120 people. At a guess, around 40% of the entire staff (admin, management, scientists, technicians) are PhD graduates. They're working in industry and reasonably well paid.
The point is that a desire to secure senior academic positions, such as tenured professor, are not the only reasons people decide to pursue a PhD.