What have you earned when you clocked in 40 hours/month (give and take) when logged in Facebook? If you are logged in because you are a social media handler of a product or a company handling Facebook pages, then you are earning your keep. This will enable you to issue ach checks when needed.
But if you are just FB-ing to read updates, look at photos, watch videos and chat with your friends, you definitely are not earning a penny from it. As a blogger, I must say that I earn traffic when I share my posts/links in my FB page. Earning in this context means monetary benefits.
What is my gist? We spend a lot of time in FB which takes away time to be more productive, to do other tasks that need active physical participation. Logging out means we get to bond more with our loved ones rather than just saying we love spending time with them. Logging out means we get to spend quiet time with ourselves.
And by the way, we made some FB people millionaires.