You don't need to know anything about a person to know that, at some point, they'll be hungry. So, if you're some company that happens to sell food nationally, you can just throw your ad at anybody. That's what I mean by "big generic brand".

However, if you sell, say, artisanal hot sauce, you'd pay more to target an affluent person that likes spicy food, rather than some random person that may be just be googling how to make macaroni and cheese.