Was wondering that and then told myself, come on, nobody would be that evil, the whole idea is nonsense. And you're suggesting there are websites out there that actually do that?
I don't think they did it deliberately, but I'd bet someone said "We could increase engagement if people didn't have to click anything to keep seeing more content" and nobody bothered to think about other design consequences of automatically expanding the content downward forever.
EDIT: A screenshot of Facebook's in mid-2013 is shown here under the "Unreachable" header https://www.smashingmagazine.com/2013/05/infinite-scrolling-...
Or straight to the image: https://cloud.netlifyusercontent.com/assets/344dbf88-fdf9-42...