A couple of things. To get to STEM PhDs, you need STEM undergrad and master’s. If you look at what degrees people pursue, STEM degrees are less as compared to o

A couple of things. To get to STEM PhDs, you need STEM undergrad and master’s. If you look at what degrees people pursue, STEM degrees are less as compared to other majors. You can’t become a AI/ML PhD with an undergrad degree in History. That pipeline needs fixing. Plus, getting college degrees is expensive. People who have a STEM degree only feel a need for advanced degree if their careers aren’t doing that well. Why would you give up a high paying job to go into debt? If things are doing great, why change anything? And last but not the least, market dynamics. If you spend 5 years to get a PHD + 2 years of Master’s, you get a higher paying job than a fresh undergrad, but people with 7 yoe get paid a lot more than that because they develop a different set of skills by then. It isn’t a very lucrative proposition for most Americans.