Earlier quoted context omitted.
"they just tack on the feature to one of their existing social products" After the rise of Snapchat Facebook tacked on stories to FB, IG, and WA.
Meanwhile snapchat pushed for weird tv shows and sponsored and featured stories, pushing friend stories to the tiny row on top. It's like they do it on purpose to alienate users in exchange for short time increase in "engagement".
Understanding these phenomena is easier when you think of it solely in terms of the bottom line.