I am sure they have done the math and for some reason it does not work in their favor by putting ads on stories, but I have had a couple of stories like the one you point out where I had many thousands of views and made only a handful of dollars. This must happen all day long with Medium. 39k high quality views would generate probably hundreds of dollars in ad revenue (I base this on a blog I run that makes hundreds of dollars on Google Adsense a month). I don't know what is holding them back. Doing some type of revenue sharing with creators would be the best option. I wish we could understand Medium's thinking but they have done so many weird things that I can't understand half of it.