I thought it started with the google algorithm rewarding more body text and high linger-time. Sites that just present info concisely are down ranked (then google extracts the concise info from long time-wasting sites and puts it directly on their search page—a whole thriving ecosystem of bullshit jobs, but at least now we can automate every part of that!)
The commonly believed reason is that a simple list of ingredients and steps would not be copyrightable. So they add fluff which can be copyrighted.