There's nothing stopping you, true. But I think you will find that nobody is going to buy software for whatever thousands of dollars it took you to make it. So the limitation in this case is a practical one, not a legal or moral one.

I can't possibly take this at face value since it's obvious that people (businesses) pay others many tens or hundreds of thousands and millions of dollars to build software for them. So, what do you really mean?

That suggests there's never been a viable market for commercial software at all, which is obviously wrong.

That's kind of black and white thinking though. No one is going to pay a million dollars for QuickBooks, but a lot of people paid several hundreds. Just because no one pays you to develop a new QuickBooks (at least pre LLM), doesn't mean there's not a market there.