There is certainly potential for to make money on social media sites and it can be the better platform. It depends, e.g. as a "brand ambassador" or "social media influencer." If you can control a certain Facebook groups that have many members there is also the potential for making money there too although it's not in the same way as owning your own forum. That's usually why those who do social media marketing and the like (optimizing and creating content on the sites of others) are different from "webmasters" who deal with running their own site. People are people. They can be very enthusiastic proponents of what works for them and feel it is the better solution and makes them feel better about their choices. I enjoy hearing about all the different ways people have been able to make something work for them.