Who is telling you that you have to write open source software? Millions of programmers around the world make a living writing software with much more restrictive licenses (including simply All Rights Reserved). I write proprietary code, and I don't feel any pressure to stop doing that. Somebody on the internet telling me that I should write open source software instead is not an issue. They can't stop me from making money writing code.
Edited to add: I don't own the rights to my code but I am fairly compensated for it. If I were to write code that I have direct ownership of, the above principles would still apply.
> CC-BY-SA-NC isn't OSI approved and you get told you're "not open source" if you try to use it or licenses like it.
CC-BY-SA-NC is indeed not open source, but that doesn't mean you can't use it.