Why no Chocolate-Vanilla combo ice cream flavor?
Not in a neopolitan fashion (i.e. separate layers) but mixed together so you get a off-brown color mixture, with hints of vanilla bean and chocolate.
Seems like every other ice cream combo on earth has been dreamt up, packaged, and marketed ...
Because chocolate ice cream is often made on a vanilla ice cream base in the commercial world (Carvel, I believe, popularized this; they used vanilla ice cream (rather than "sweet cream ice cream") as the base for most if not all of their flavors). Might not visually look like it, but food coloring doesn't necessarily indicate actual proportions....
If I may offer an "ipse dixit" on this topic...
I think there are several reasons why "Chocolate Vanilla" is not a marketed flavor:
1) There are generally two different camps of ice cream eaters when it comes chocolate and vanilla--those who prefer chocolate and those who prefer vanilla. To mix the two together would really make something more like...
2)Milk chocolate ice cream! Less intense than dark chocolate, milk chocolate ice cream has a following all its own. To combine the two flavors in the fashion you describe might make the chocolate flavor too weak to be enjoyed by chocolate enthusiast, and the vanilla too muddled to be enjoyed by those who prefer vanilla.
3) Having worked in restaurant kitchens as a pastry chef, I will admit that one of the "secret ingredients" in many chocolate ice creams is a bit of vanilla--not vanilla bean which would show its telltale flecks, but high quality vanilla extract or vanilla paste which enhances the chocolate flavor without being too vanilla-forward.
4) High quality chocolate has a complex flavor profile. Adding a noticable amount of vanilla or mixing it with vanilla ice cream which usually has a "floral" profile can just about ruin a good chocolate ice cream. Yes, this is an opinionated statement, but it's my post and "he himself has said it."
You could always do what I do when a flavor I want isn't available in a container--I make it myself! Who knows, the next time Haggan Dazs has a flavor contest, it could be yours that wins!
Actually, when I was a kid my dad's favorite ice cream order was always a scoop of vanilla and a scoop of chocolate, served side y side. He'd eat some spoonfuls of each and some together. From him I learned that vanilla is a wonderful flavor enhancer for chocolate, as mentioned in the other posts. (Needless to say we all preferred vanilla-chocolate-chip to chocolate-chocolate-chip.)
The side-by-side, neapolitian-without-strawberry concept does show up, more or less, and with added stuff, in Ben and Jerry combination pints like "Half Baked" and "Everything But The . . "