People don't understand that their news feeds are algorithmically generated based on people and content they previously interacted with. I cannot stress enough how bad this is.
SM companies do this to keep you on their platforms, looking at their ads. They assume if you engaged with "x" FB page 4 times last week then you must like "x" FB page so they'll keep showing you more of "x" FB page, since you like it, and hopefully you'll stay on FB longer.
The other unseen force that keeps us glued to our feeds: the user interface is engineered to be addictive. It's a slot machine in your pocket. People embrace the "endless scroll" because it's designed that way -- and it's good for business. 
Also we tend to stay in fairly stable social circles and the people in those circles are who influence us most. Natural human behavior reinforced by algorithms. You engage with people you have things in common w/ so the algos show you more of those people. futurelearn.com/courses/social…
