All of the dozens of US STEM PhDs I know from recent decades had to pay their tuition by working as TAs, RAs, or usually both. They didn't walk in the door wit

All of the dozens of US STEM PhDs I know from recent decades had to pay their tuition by working as TAs, RAs, or usually both. They didn't walk in the door with a trust fund, work through the coursework, and then write up a dissertation. I'm not sure that's even a possibility in most STEM fields: you need access to millions of dollars of ultra-specialized equipment which you can realistically only get by working in an existing lab, which means being an RA.