The insular mentality [of comic book companies] remains. By and large the philosophy is still to create almost exclusively for the audience that’s already here or the one that used to be here. Women couldn’t possibly like superheroes (despite the gads of evidence to the contrary). Children would never buy superhero comics (despite the booming kids and all-ages comics market and kids’ almost-unanimous love of superheroes). When they’re asked why they don’t try harder in these areas, they say that they’ve tried in the past and they just never work out. Why don’t they work out? Because, no matter how well-meaning, they have usually ended up being sabotaged on some level. Budgets are miniscule, or start off reasonable and then vanish when there isn’t instant success. Almost always, the marketing is done to the same audience who has steadfastly resisted reading anything beyond superheroes or similar male-targeted fantasy/adventure. Why expect anything beyond a small percentage of crossover? ... DC and Marvel largely don’t know how to market outside the superhero audience, and when they do usually give it such a miniscule budget that penetration is minimal. Conventional wisdom would say to hire a marketing firm that does know how to reach the target demographic, but of course that requires money.
Does this sound familiar? To my ears, it does: it's the same problem I've touched on before about how it's easier to sell what you know to the people you know than it is to sell something new to anyone at all. Why? Because the latter requires, oh my gosh, work and money. More than that, though, it requires risk, and that's the one word you never want to speak out loud in front of a publisher lest you have them whip out the garlic and crosses.
Another point made later on in the same piece was even more striking: the fact that Marvel and DC have between them some two hundred and forty (239, actually) comic titles, and yet cater to the same core market over and over again. Image, by contrast, has far fewer titles but far more diversity.
My wild-ass guess is that diversity is largely a function of the curiosity, taste, and boldness of the people in charge. I've compared it most often to the record labels of old — the Motowns and Atlantics and even Wax Trax!s, the rosters of which were essentially reflections of the taste of the Berry Gordy, Ahmet Ertegun, or Jim Nash that was in charge. That sense of taste enhanced, however subliminally, the sense that what you were experiencing was a curation, a one-to-one connection between the folks who ran the label and the listener buying their records.
Now what happens when the person in charge is little more than a glorified accountant? Ask your local movie studio for directions.