"Regarding my initial point, I think software falls under copyright solely because its written"
No. That's a degree of misconception that I can't fix in an HN post. Copyright has little to nothing to do with the medium in which an expression is fixed. And with all due respect, the rest of your post is so muddled w.r.t. what copyrights really are that it's hard to even address what's there. (I truly mean "with all due respect", but I also truly mean that it is very muddled.) You really ought to spend some more time studying the topic, including such basics as what exactly copyrights are and what, exactly, they cover, and why.
What I meant was, "it's fixed somehow". I assume the original reasoning for why code is copyrightable is that when I write, say, a book, that is copyrightable. Code is written down just like a book is, so it follows that copyright will apply. I'm not saying that's the legal reasoning. I'm saying that was probably the initial gut-reaction to why copyright should apply to code, and the legal reasoning came afterwards.
I have spent time with the various forms of IP, and I feel I have a pretty good grasp of what copyright is. I can't correct any misconceptions unless you point them out - although I have a feeling it's more that I did a poor job of expressing myself.
Attempt the second: with non-software inventions, you can have a copyright on the documents that explain how to build the invention. You can have a patent on the invention itself. Software can be both copyrighted and patented. You object to this because it's the only instance we have of something that can be both copyrighted and patented - it's a unique exception. I responded to this objection by pointing out that software is also unique in that what you use to describe exactly how to make the invention is the invention itself.