[grosskur]

For me the main reason is consistency. I can write apps in Python, Ruby, node, etc. and configure them all the same way.

The envdir program (from daemontools) is useful for setting environment variables in a shell-agnostic way, e.g., run your app with:

  envdir ./env python app.py

See also

http://12factor.net/config

[ceol]

Another good point. Thanks for the link, too!