Most of the internet runs on a Feudalist based system, which is commonly described as a “walled garden”, a closed, hierarchical, centralized database.
In other words, Facebook is like a big garden where the content is the flowers, and you can both admire the existing flowers of the garden as well as plant some of your own beautiful flowers (aka dank memes). The owner of the garden – Mark Zuckerberg – controls what kinds of flowers you can plant, what flowers you see on your end of the garden, and what weeds he’s going to poison and remove.
Just like a real garden, it costs a little money to transport waste products to the tip, so it’s cheaper to store content in the compost bin rather than take it to the tip to be removed forever. This article from WIRED shows just how many old flowers Zuckerberg has stored away in his compost bins and green houses.