I think that the reason is more psychological than anything. People who deal with information become unsettled psychologically because they are doing something

I think that the reason is more psychological than anything. People who deal with information become unsettled psychologically because they are doing something that is very unnatural, and so new note taking apps is a meaningless gesture that makes them feel that they are under control. Of course, that's not the entire explanation but it does explain partially the proliferation of note-taking apps beyond the basic ones.