Because i have worked with many math phds who lost their youth to something that they could not make a living on (research positions at universities are few and the competition is intense) and were writing C++ implementations of derivatives pricing models for a (comfortable) living.

I am not trying to discourage you, just a different perspective.

Well, luckily I'm not doing this in the hope of increasing my earning potential. It's an entirely separate pursuit. I have no doubt that what you're saying is true, but I don't think I'm bothered by it since it's not my goal.