title: Why nginx are required to be run on docker sometimes?
body: <p>I'm learning about docker and nginx(jwilder/nginx-proxy, ...). 
  During configurations, I couldn't figure the reason out why I should install nginx on docker. AFAIK, It is possible to access containers using their exposed ports and only one nginx on my real host can serve them all. 
  Which advantages can be expected when nginx is run as a container?</p>