Discussion: The importance (or unimportance) of Warming up

So, this is me setting the precedence of a discussion, and if it ends up not working out so be it, but what are your thoughts on warm-ups?

There are those who believe they are not only necessary, but that certain warm-ups will key you in to the right mindset, others believe they're just there for energy, and still others don't think they're necessary at all.

Put your opinion in the comments, and feel free to write your own discussion prompt.