Why is serving static files insecure

This might be a stupid question and have an obvious answer, but I was testing my 404 and 500 error handlers meaning that I had to switch debug to False. I went to Django admin page and noticed that static files are not being served.

I understand that they should be routed through Apache as serving static files through Django is insecure. However, I don't quite understand why is it a security risk to serve static files through Django directly?