Mathematicians who write software are no more likely to be "truly making the world better" than those who prove theorems and teach hundreds or thousands of students every year.
I'm not saying anything about Stein here. He's a rare mathematician: strong on theory and practice, a passionate advocate for his causes, and a respected teacher. But there is a danger of missing the real point here -- most good things don't get funded or recognized. This has gone on for centuries. The funding situation now in the US (for both theory and practice) is better than it has been almost everywhere for almost all time.