The answer I formulated for myself back then still holds, twenty-something years later: I'm one of those people who is interested in everything, and studying English allows me to study everything. No, we don't spend all our time studying grammar (though actually I wouldn't have minded doing more of that, but then I'm pretty geeky even by English major standards).
If English isn't just about grammar, what is it about?
English* is about language, ideas, stories, and what it all means. (*Caveat: This is true of all language, not just English, and of expression in all cultures, not just English-speaking ones. But I'm in an English-speaking culture and English is my field, so I use the term "English" here in the broad disciplinary sense, not in the sense of "English only." If you're a specialist in Spanish or French or Mandarin or any other language--or if you work in a humanities-related field other than a language or its literature--please read this as applying to you also.)
Language. Try studying any supposedly more "relevant" subject without using language (duh); it's central to almost every aspect of human existence. (For now, I'll sidestep academic debates regarding the extent to which language constructs our very reality and assume we can all just agree that it's central.) What could be more educationally relevant than the in-depth study of a culture's language and all that it expresses?
Ideas shape the world; doesn't the idea of something have to exist before that thing can be brought into material reality? (Last month I viewed the Wright Brothers' plane at the Smithsonian, and the exhibit made it clear that the discovery of how to fly had to exist first as an idea.)
Stories: How else do we make sense of our lives? How else do we teach our children? How else do we disseminate knowledge from one generation to the next, build social bonds within and across our communities, make sense of our personal and collective tragedies and triumphs?
What it all means: Isn't that the most relevant question of all? (And no, English teachers do not go around looking for "hidden meanings" in things--the fact that meanings are not actually "hidden" merits its own post and is something I'll get to later.)
So considering that English is about things that form the very center of human endeavor, why is it English that ends up in the institutional basement? (In some cases that location is merely metaphorical; in some cases it's also literal.) Considering that we study and perpetuate what lies at the core of most other creative and intellectual pursuits, why are we the ones being treated like weirdos? Maybe it isn't the English majors who should be grilled at social gatherings about why we majored in "that." Maybe it's not the English teachers who should be mocked (and underpaid). Maybe it's not those in the humanities and liberal arts who deserve to become the butt of national jokes regarding the addition of French fries to a fast-food order (though we also ought to cease mocking those who serve fast food for a living--snobbery is always ugly).
If humanities cease to matter in this world, what kind of world will it be? Suggested reading list here: The Giver, Nineteen Eighty-Four, The Hunger Games, Fahrenheit 451, and just about every other dystopian novel ever written. If you want to know what a humanities-free world might look like, countless authors have already done the work of imagining it for us. Hint: It isn't pretty.
It may be that right now, not enough people understand why we're necessary. But we are.