For a person that isn’t from a wealthy background already, it’s hard to justify the path of academia when a more lucrative path has much more potential to be life changing for them and their family.
There are indeed people with CS PhDs at Google and Microsoft whose primary job involves publishing papers rather than building applications. But that's not the norm.
also, he might include that STEM professors earn higher than other academics and have many opportunities to earn high rates of consulting pay, and or spin off to found companies, etc.