Jessie James Decker knows the key to selling a cookbook is to get naked because it incorporates two of life's biggest pleasures: sex and food. Those who would buy the book regardless of the nudity are rewarded with her sexy self, and those who only purchase it for the photos are rewarded with simple, tasty dishes they can easily whip up. Win-win.
On the other hand...
Eric Decker knows if he gets naked, not only does he reach a different audience, but his loving support for his wife will drop panties all across the country. Why is this important? No, not because he's interested in getting in any other woman's panties, but because he knows nothing is hotter than a man who drops everything to sit like his wife.
In this case, that demonstration of love directly translates to sales. If a woman was unsure about purchasing the cookbook, all it would take is one look at that perfection of a body to decide, "I need this book because I need to get me a man like that!" It's kind of like the tradition of the engagement chicken but instead of some old-timer family recipe guaranteed to get your man to propose, his book-covered dick makes you want to cook whatever the hell she cooked to get pressed up against that bod.
After all, aren't we all just looking for that unconditional support to get weird with?