I think the attraction for writers were network effects. It's kind of like YouTube for text content. Recently, I watched a video about the game Crokinole on YouTube. Afterwards I got a bunch of suggested videos: other videos about Crokinole, videos about other board games, videos about making your own Crokinole board ...etc. Medium does (or was supposed to) do something similar for articles, which in turn should lead to more views on your content.