For 44 years, PBS’s Masterpiece franchise has brought high-end Britain TV programs to American audiences. While the ultra-successful Downton Abbey comes from an original screenplay, many of Masterpiece’s shows over the years have been adapted from great works of literature. And the vast majority of those great works of literature, unsurprisingly, have been British.

But every so often, an American novel—like James Agee’s A Death in the Family or Willa Cather’s The Song of the Lark—has been turned into a Masterpiece. On Friday at the Aspen Ideas Festival, Rebecca Eaton, the longtime executive producer of Masterpiece, said she wished that the program had tackled more U.S. authors over the years. “The reasons that we haven't are twofold,” she said. “One is money, the second is money. And the third is money. Also, the dark nature of American literature, which is something to think about for a moment."

The money stuff: Hollywood has locked up the rights to most major American titles that aren’t in the public domain. That’s not the case with great British literature, partly because much of is older, written in the 18th and 19th centuries. Eaton, in her hour-long discussion of the history and future of Masterpiece, additionally said that the UK just has a more resources at the ready to make costume dramas set there: “They have all the carriages, and all the frocks, and all the locations.”

But Eaton also theorized that American literature is often too dark, too weird, for Masterpiece and maybe for TV more broadly. “This is a huge generalization, but [American novels] have tended not to have all the elements that make it good for television, whether it's too interior or there's not enough action,” the Boston-born Eaton said. By contrast, “the Brits tended to write more colorful stories rather than the darkness and struggle. Dickens and Trollope certainly knew how to write sequels, books that would make good ongoing series again and again. And the greatest love stories are in the Wuthering Heights and Pride and Prejudices. I don't know what our equivalent is.”

While an fan of the American canon might bristle at those comments, consider the history of literary adaptations. Whereas English Literature 101 authors like Shakespeare and Jane Austen have inspired a host of well-loved movies and TV shows, often, when talking about American writing turned into viewing, you end up talking about “genre” works: science fiction, Westerns, comic-book films, The Hunger Games. Most American novels widely regarded as classics have been made into movies or shows at one point or another, but many have yet to receive an on-screen treatment that lives on in the cultural memory. The 1956 adaptation of Moby Dick received some strong reviews upon its release, but is rarely seen today. Hemingway’s movies, for the most part, have been handled spottily by Hollywood. The 1995 The Scarlet Letter flopped; recent screen versions of As I Lay Dying and On the Road received middling reviews and never went to wide release.

There are, of course, huge exceptions to the idea that American lit doesn’t work in a visual medium—The Color Purple, To Kill a Mockingbird, Little Women, and East of Eden, among others, made a greater cultural impact when seen on screen. Eaton said she’d be interested in revisiting Gone With the Wind as a miniseries, if it were not for copyrights issues. But as for perhaps the most famous work of American literature that has been repeatedly adapted over the decades, Eaton seemed mystified. “The Great Gatsby really is a very enigmatic story—what is this really about?” she said. “It amazes me that it keeps getting taught.”