Why is STEM important? (a layman's view)

A few weeks ago I was invited to speak at the Indianola STEM Symposium and Appreciate Night about why STEM is important (particularly to the audience of mostly high school kids). Hmm — why is STEM important? Why is it important to high school kids? I *accept* that STEM is important — we hear that all the time — but its hard to delineate exactly why its STEM is important.