A lot of these sign languages were developed before the Internet or any easy mass communication via video. Each region developed their own language, and at this

A lot of these sign languages were developed before the Internet or any easy mass communication via video. Each region developed their own language, and at this point it's so ingrained into local cultures that trying to get every sign language user to switch to some international language would be like trying to get everyone to switch to Esperanto. It's not happening.