Universities make much more money off their Masters students, most of whom are international, and pay full tuition (or someone does for them).
For MIT EECS (largest dep't on campus; ~700 PhD students) there's no Masters-only people (except MEng students who continue for a 5th year from undergrad). The department only accepts applications to the PhD program and funds its students accordingly. They probably lose money over their international students because none of them qualify for NSF fellowships, etc.
It's a scam.
The Ph.D. is the real graduate degree in US schools. If you get a MS, people who know the system expect that you flunked out in quals (it's the parting gift for those that couldn't handle the work). Terminal MS degrees at serious schools are just outright selling prestige to the naïve.
A MS from MIT or Stanfurd is much, much less prestigious than a BS degree from the same school and requires less academic rigor.
Personally, a research oriented MS degree allowed me to work closely with a researcher and contribute to that research leading to paper publications and a thesis. The goal of the program seems to have been to allow people to get a taste of doing research and then move on to a PhD program if they found that appealing.