I noticed that most of the books and tutorials on Django make it very clear that use Django development server as a normal webserver is not OK. But some state that other webservers are optional, that we can use Django server to put the website on the web for everybody to see.
But why exactly? Why do I need (or not) to use Apache, Lighttpd, Nginx, etc. in front of Django - WSGI?
Is Django server not safe in some way? If so, how it is unsafe exactly, and why can't Django just come with a more robust webserver (out of the box, ready to use)?
How exactly those webservers help Django? *I know that those webservers have very useful mods, but AGAIN: couldn't Django just come with a safer "mod-able" webserver?