This question was prompted by answers and comments on this question about PhD student funding.
I am under the impression that STEM Ph.D. graduate students, when accepted into an RU/VH university in the United States, will typically be funded for at least 5-6 years, depending on the average length of Ph.D. in the specific field, by either TAs, RAs, a mix, fellowships, etc.
I understand that my university, the University of Arizona, has shirked this duty in a legally binding sense, but is this impression wrong?
If it is, why would I (or any other graduate student) risk having to find a job in the middle of a Ph.D. in order to "pay the bills?"