Here's an interesting factoid from the Hollywood scene that gives insight to the rise of CBA fiction:

Of the twenty top-grossing films of all time, not a single one is rated R. Of the top fifty films, only five are rated R. Clearly, Americans want family fare they can take the kids to. And yet, as Anschutz noted in a recent speech, since the year 2000, Hollywood has “turned out more than five times as many R-rated films as it has films rated G or PG or soft PG-13. . . . Don’t these figures make you wonder what’s wrong with Hollywood just from a business point of view?” (from "Lighting a Hollywood Candle")

Hollywood is bent on pushing rated R media down the throats of consumers, even if it goes against the grain of business sense to do so. And to a degree, mass-market (non-CBA) fiction is following a similar trend.

Why is CBA fiction's popularity rising so quickly? In part it's because there is no rating system on secular books. You pick up a random fiction novel at Barnes and Noble and you are quite possibly going to have the literary equivalent of an R-rated film in your hands.

Buy CBA fiction and you have something that is more G or PG oriented.