Why do I generally dislike chocolate ice cream but love vanilla ice cream mixed with chocolate syrup?

I've always wondered this. My favorite ice cream is vanilla, I'm one of those stickers against the idea of thinking of it as the 'default' option (vanilla is a flavor!) but adding chocolate syrup has always made it better. This is in clear spite of the fact that I don't like chocolate ice cream much. Is there something different chemically? Is it just, the taste of vanilla bean itself? Why does added chocolate taste better than chocolate already mixed in?