Why is the Class B forum so dead?

I am a member and active on a lot of diverse message boards. They are all down and dwindling. I think it is Facebook groups that have done it. To me it is way better than Yahoo groups and Facebook is getting more robust in its capabilities especially with smartphone use. The day of the independent message boards is dying. I've seen many forum platforms come and go for over 30 years. This type of messaging board came popular around 2000. Before that it was AOL, Compuserve and Usenet in that descending order. If anything hastens RV.net's demise it will be its antiquated messaging software.