It's viewed as a DRM measure. Recipes are not copyrightable unless they are attached to a story. It's probably an urban legend, but can't blame poor food bloggers from acting on it.
Based on this reasoning, the United States Copyright Office Compendium, the Office’s manual for examiners, states that a mere listing of ingredients or contents is not copyrightable, as lists are not protected by copyright law (chapter 314.4(F)). The Office has also stated that a “simple set of directions” is uncopyrightable.
In addition, courts have found that recipes are wholly factual and functional, and therefore uncopyrightable. As the Sixth Circuit described in Tomaydo-Tomahdo, LLC v. Vozary, “the list of ingredients is merely a factual statement, and as previously discussed, facts are not copyrightable. Furthermore, a recipe’s instructions, as functional directions, are statutorily excluded from copyright protection.”
