I'm not sure we have a glut of PhD's at all. At least not in fields where there is actual research in industry. I work in industry on a team where almost everyone has a PhD and those that don't have a Master's degree (or two). The team I'm on publishes research, reads papers regularly, attends research conferences, has visiting professors and researchers give talks, but also ships product. Maybe CS and AI is an outlier in terms of having huge demand in industry (relative to the work available, there is a huge shortfall of AI PhD's), but I wouldn't be surprised if much of industry is like this. Plenty of people go into a PhD to go into industry in a research-oriented role. The claim that we would be better off with a less educated society is so extraordinary it requires extraordinary evidence. A handful of cherry-picked data points and a skewed interpretation is very unconvincing. Yes there is a cost in an investment of time. But for many PhD students these are happy years they remember fondly for the rest of their lives, even if they end up outside academia. If we have an actual genuine glut, show me a survey with good methodology showing that most PhD graduates regret doing their PhD's. We don't have anything close to that.
I work at a small unassuming civil engineering company and we have plenty of PhD's here. Within most areas of science and engineering I'd say that getting a PhD because you want to go onto industry is the norm rather than the exception.
