The steam that blows the whistle

What's the meaning of 'The steam that blows the whistle can't move the train'?

A steam train runs by boiling water to produce steam which makes the engine turn. When you blow the whistle, you let some of the steam out through the whistle so that particular bit of steam is lost.
In other words, it's a waste of energy to talk about doing something when you could be doing it instead.