Look at the specs. Chocolate has far more kilocalories than vanilla. And flavonoids. That's real innovation.
Who cares about specs? It's about marketshare and profit. Vanilla is winning.
According to a recent survey of International Ice Cream Association member companies, vanilla remains the most popular flavor among their consumers.
http://www.idfa.org/news--views/media-kits/ice-cream/ice-cream-sales-and-trends/
Besides - vanilla is more flexible. You can add anything to it and it just works. Chocolate is a walled garden. Sure it might have great taste - but it's limited in function. You simply can do MORE with Vanilla.
Now don't get me wrong. I eat both Vanilla AND Chocolate Ice Cream. I just pick the flavor I like best that accompanies my meal. I'm glad there's a choice.