copyright law doesn't have to make sense. a recipe isn't a creative work, it's a list of ingredients and potentially the mechanics of putting them together. The actual recipe cannot be copyrighted. There are a lot of articles that are factchecked with a search for "recipe copyright". The rule of thumb is what i stated, in order to protect one's work on recipes or a compilation of said, one has to insert prose and other media.

Anyhow the main point is that recipe sites being the way they are has nothing to do with SEO, it's the "generally accepted practice" of protecting your work.