Tomatoes and potatoes can be grown almost anywhere, making them "native" vegetables once they're discovered. A vegetable needs to be available in quantity at low prices for cooks to be experimenting with them and for recipes to enter the public domain. This explains why there are more cocoa recipes in countries where cocoa is grown and less where it must be imported. Candy sells for a higher profit than other food, making production of candies from expensive ingredients economically viable, which leads to more experimentation with candy recipes. There are far more peanut and banana recipes in areas where those are grown than in Europe, for example, so it's not just cocoa.