Take it as an "infrastructure"/"swiss army knife" for hosting and deployment. Most of its features are still topic of research in autoscaling,management, tuning and so on... Most of the users do not need that features, but others (like the Emperor) can be useful for everyone. Regarding the additional layer, is something required, as your code/framework need a way to communicate with the webserver and being healthy. Nginx's mod_wsgi is an old non official module, very funny, but it works in a very different way embedding python itself in the nginx core.