I always thought it was to push the useful information as far down the page as possible so you have to scroll by a bunch of ads to get to it.

This is worse with web but is old as time.

It used to be common for ingredient sellers to issue recipe books that would extoll the value of their goods, trash their competitors', and the recipes would usually include the ingredient even if it didn't do anything for the particular food you were trying to make. (E.g. "our flour is pure, unadulterated, and not bleached using toxic ingredients unlike our competitors who also eat babies", which was a more effective marketing tactic before the existence of food regulatory authorities curbed the worst excesses.)

The recipe on the side of the box is a much smaller-scale version of this.

It's also a sales tactic. Mary Jo Rose is selling you her story so that you will buy the idea that you should subscribe and keep reading her posts even if you have nothing to cook, and eventually use her Amazon link to get 10% off paper towels.

yes, that would also serve SEO - longer on the web page + more content viewed = greater "engagement"

Even regular cookbooks these days will have a bit of fluff before the recipe for this purpose. Though in a cookbook pictures of food also serve this purpose.

Some examples from cookbooks: https://www.maangchi.com/wp-content/uploads/2015/01/mul-naen...

https://www.cookbookdivas.com/wp-content/uploads/2021/10/Cel...

I bought a $5 keto recipes book at my big-chain grocery store's checkout.

It's a lot easier to just try a new recipe when it's not tied up inside a 100-comment Reddit thread debating its nutritional value.

I don't mind that so much because it's easy to skip the fluff - you can find the ingredients and method in under a second since no scrolling is involved

I also wouldn't be surprised if the fluff is there because it was originally written for web and chanced upon finding a publisher