This is mostly because a lot of people got useless degrees that don't result in high paying jobs, not because of some intrinsic cost of education. The number of STEM degrees awarded [1] is far outstripped by non-STEM degrees in both number of degrees awarded and growth rate [2].
I am merely saying the current private student loan rate is 3-5%. It is not possible for substantial interest to accumulate at that rate, particularly if you factor in inflation (6.8% YoY this month...)
[1]: https://www.nsf.gov/nsb/sei/edTool/data/college-14.html [2]: https://nces.ed.gov/programs/digest/d12/tables/dt12_310.asp