This excellent CJR article (from earlier this year) "Little Murders" by Jesse Sunenblick discusses censorship of provocative artwork. Often, sophisticated idea-oriented illustrations are being replaced by heavy-handed and even crass material because it's not as dark or disturbing. Sunenblick concludes that Marshall Arisman has hit upon the reason:
Something an editor at Time had said stuck with him over the years: We're a society that's willing to read all sorts of things about violence, to look at photos about violence. But we're not willing to look at artwork about violence.Sunenblick describes rejected (or altered) work by such luminaries as Arisman, whose rejected Time cover on the theme of capital punishment appears above, Robert Grossman, Brad Holland, Mirko Ilic, Stephen Kroninger, and Steve Brodner.
Arisman says he asked why that was so. The editor replied that when people look at photos, they think they're looking at reality, not a statement by the artist. But when people look at artwork, they think the artist invented it.