Frontend frameworks developed in response to the need to develop/maintain very complex browser-based applications like Facebook across a large team of developers. AirBnB/Reddit have dramatically more complex user behavior and are much more input- and media-oriented. You cannot wait on round trips to the server for user interactions, and you cannot just do hybrid client/server the old jQuery way on big applications because you get spaghetti code.
Comparing Reddit and Wikipedia is like comparing a motorcycle to a bicycle. They are different, with specific strengths and weaknesses. Both design/engineering paradigms have a place, imo.