Good answer!
Primarily, it's to do with complexity. It's pretty easy to brew a hoppy IPA: Mash some pale malt, add hops to taste, ferment. It's simple.
When you start adding more ingredients, the complexity rises, and the more complex a thing/process is, the greater the possibility it's going to go wrong. There's a reason why K.I.S.S. is an axiom.
One of the complexities which make hoppy dark beers difficult is flavor and perceived bitterness. The darker roasted grains have a bitterness all their own, and a very pronounced flavor. It takes a lot of tweaking to emerge with a recipe that's worthwhile.
Complex flavor is a difficult target to hit. The more flavor constituents present in the food being tasted, the greater the chance it'll all go wrong.
What sort of analogy can I make here? Hmmm...
It's like paint. If you take two or three colors, carefully choose the amounts to blend, you get another color. It's pretty easy to get purple from a bit of blue and a bit of red.
What do you get when you mix seven or eight colors? A sort of icky greyish brown. No matter how carefully you choose the starting colors or the amounts thereof, you get icky greyish brown.
Taste works the same way - if too many flavors collide, it's just "meh" at best and "yuk!" at worst. That's why beers like Imperial Stout tend to avoid flavor hops - added to obviously perceptible levels - and instead rely on the roasted malts for flavor. Hell, it's hard enough getting the roasted malts figured out! Adding
another]/i] flavor, and suddenly you're spinning too many plates.
That's why many CDA recipes use a debittered black malt like Carafa for color: There's no flavor contribution, it's just color.
You could just take a strong Porter recipe (OG ~1.065) and dry-hop the bejeebers out of it. But that's risky; you don't want much more than a hint of roast-malt flavor in CDA, and you don't want Crystal-malt characteristics at all. Plus it needs to finish dry. I'd rather brew a grist consisting of pale malt and add some Carafa II or III (or probably Sinamar). In fact, I'd brew my standard 19th-century IPA recipe (all pale malt), add enough Sinamar to make it black, and use Cascades instead of Goldings. That's it.
Check out the BYO article on the style.
One of the reasons why you're not seeing many recipes is that it's a relatively new style. Give it time.
Cheers!
Bob