I think people are really intrigued by the idea of quick money that's why they usually find themselves quitting when they don't see success quickly...
After writing a 165 articles I'd say I've barely seen any success, but I don't think I'll ever quit, because I see it an investment within myself.
When I write on Medium, there's immediate feedback as to my performance. When I write a good article, I make good money, when I write a bad article, I don't make anything.
But for my 3rd article I'll know what to do, and what not to, and that makes me a better writer.