The best reason to go to grad school is probably if you want to have a career in the academy.
I am really irritated by the “Just Don’t Go” school, because I think it reflects a kind of cultural turn away from valuing the contributions of scholarship and intellectualism.
That is, I think people say that you don’t have to go to college or to grad school because, for people who are highly motivated and self-directed, you don’t have to: you can find or make ways to do interesting work and share it with others outside of the university system. In other words, they are right.
However, every discipline has deeply layered (sometimes deeply sedimented) histories, methodologies, and ways of talking about what they are doing, and much of this culture of scholarship does not seem to me to make itself available outside of the academy. (To put it in familiar terms, think of Eric Clipperton in Infinite Jest as an Independent scholar). Without the institutional weight of the academy—whatever its drawbacks—you will not be trained in the context of a community.
That being said, it’s not like grad school is not isolating, and lonely. That’s why it helps to come in with some idea of what you want to get out of it. It will give you a sense of the light at the end of the tunnel. If you value intellectualism, graduate school can help train you to argue in a way that meets certain scholarly standards—standards that even people doing other kinds of intellectual work are not always held to. Also, it can train you to interrogate and revise those standards. Part of what gets to me about “Just Don’t Go” is the way that tends to dismiss the value of rigorous argumentation.
Generally speaking, I love my classes, I am encouraged and supported by my professors, and I feel like I get to do a kind of intellectual work in grad school that I would not get to do anywhere else. I also like teaching, and I enjoy working my students, even though so far I’m only TAing for American literature classes. It is also challenging, and demanding, and I’ve definitely made sacrifices to get to do this. But so far, I’m glad I did.