I was a graduate student during the 1970s and was the recipient of a tuition waiver and other financial aid. Had this been taxed as income, I would not have been able to complete my Ph.D.
It is said that a basic principle of taxation is to tax activities you wish to discourage and not tax activities you wish to encourage.
I worked all my life as a biomedical researcher and inventor and in recent years as an author and educator. Thus the question for our policymakers is whether these are activities that the government wishes to discourage.