1) Seeing your code do what you told it to do, regardless of whether it makes you any money, is one of the most satisfying experiences I know.
2) And seeing your code f*up is a reality check. Good for the soul. And debugging can be an adventure in itself.
3) Your mind is expanded.
4) You learn to think logically.
5) Maybe you get a job because of it, maybe not. But why should you not learn something new?
A lot of great replies
Frankly, I was thinking more existentially. Coding for coding's sake. Coding is one of the ways that I relax. I may never write a profitable strategy, but I'll code them anyway. Probably won't run them ...