Encore!

This has been argued countless times before but sod it, I'm still asking.

Who decides whether or not to have a "Curtain Call" or "Encore" as some would say?
I've had countless answers such as :

-->The conductor (usually also the MD) decides

-->The Stage Manager decides

-->The guy/gal pulling the curtains back and forth decides

-->The cast decide

: these decisions, of course, are based on how rowdy/quiet the audience has/have been.
Any more answers or arguments against the 'choices' mentioned? I can't make up my mind....