Earlier quoted context omitted.
"your code is a trade secret protected via contracts" isn't enough to replace copyright because the contracts are only enforceable to the signing parties. Let's say you write some software for your employer and they sell the product to several customers with a contract not to distribute it. However, the product appears on some pirate website anyway, and you can't identify who allowed the product to be leaked. Once it…
Yeah, I'm assuming most people here aren't selling proprietary code to customers directly. I assume most professionals here work somewhere that sells SaaS or uses the software they develop internally only.
Almost my entire career was spent on such custom software. The rest was internal software. And even that one I was doing as a contractor, so in a way we could argue it was custom software even there.