Grad students are essentially like employees, just with shitty pay and a higher dependence on the goodwill of their bosses to get their PhD. A large part of scientific research in academia is performed by grad students.

To compare this with an area HN is more familiar with, the equivalent to a grad student would be a junior developer fresh out of college in their first 3-5 years. Of course they don't know everything yet and they need some education and mentoring. But that doesn't mean it isn't a real job they do.

The job grad students do is roughly the same they'd do later if they stay in research.

Being an RA, at least, is very skilled labor. I’d say the job is 80% work and 20% learning academic process and social mores from your advisor.

Why is it relevant that outside of their capacities as employees of Harvard they are also students of Harvard?

OK then quit and work for an employer that pays you more.

Why do that when you can go on food stamps and have the tax-paying public subsidize labor for one of the wealthiest institutions in world history?

In many countries they are considered workers and have all the social benefits of regular workers.

As a teaching assistant before and a research assistant now, I say technically it's a job.

You're expected to perform atleast 40 hours of research, often if not 1.5x more. Experimental research involves setting up and conducting them, while theoretical research involves standardizing the set of rules that one should seek in an experiment: modeling. All works involve literature review, writing, designing plots, coming up with scientifically sound creative ideas. All that with tight deadlines too.

I don't see why this should be any less than a job.

I definitely worked harder when I was a grad student than now as a software engineer who finds time to slack.