Okay, let's say this: after years of hard work, you write the GAN. It's full of great characters, a great storyline and love and hope and sex and dreams, as great lines and thought-provoking ideas. In the climax, as an honest part of his/her character -- the MC goes off on a 2000-word diatribe about American Imperialism, and that the Sept. 11 hijackers had the right idea. It's a point in the book that you wanted to make when you started, but not the only one.
You get an agent, who, in your first conversation, suggests that you remove the speech, that the book doesn't need it. You decline. The agent says okay and submits to publishers who love it, but ask you to remove that scene saying, "We can't sell it, we'll be blackballed and so will you." You refuse, and the agent releases you from your agreement.
Had you dropped the scene, your book would be published and all your other, great points and your great characters and your great story would be out there. But since you didn't want to adjust to your audience, it's not. How is that beneficial to anyone?
I think you're trying to make accessibility a bad thing. You've mentioned Wallace -- he's an example. To most people, Infinite Jest is unreadable, and his other works even moreso. He may have been the greatest writer of our generation (I'm not saying that because I'm one of those people who, even on a sailboat with nothing else to read, couldn't finish it. Same thing with the post-office one), but because he was so enamored of writing literarily (and in my opinion, indulgently, which is what a lot of literary writing turns out to be), only a relatively few other people know. He didn't want to adjust to what people wanted to/were willing to read, and in the end it cost him an audience he could have had.