There is absolutely no incentive to make quality posts or tweets in FB or Twitter, so there is no continuous improvement in the quality of the media.
One of the amazing parts of Stemmit is that over time, the quality of the posts will continuously trend higher! I am learning to take better pictures, next I will work on formatting posts and improving my writing skills. I've been on Facebook for years, and I have never even thought about improving the quality of what I put there...
The other amazing part of Steemit, is the number of users who are working together to make us a stronger community. Achieving success by helping others to achieving success. Perfect!
Yes that is why the posts are so different and shouldn't be compared. Theres no reason to write long, well researched articles, on facebook. Or even a good way to do so.