I'm not, I get what they're saying. If I want to eat pie, I need to bake one first or find someone to bake it every time. If I want to use a software, I only need to write or find the software once; then I can keep using it indefinitely. Therefore, the common assumption is perfectly justified. Most people who write software do so to create something that isn't already available.

That said, I still agree with the post. Justified or not, the assumption is frequently wrong. Coding is fun for its own sake.