From what I've seen, your approach to LLMs is exceedingly rare, so I suspect it's one the people who care about watermarking aren't very concerned with.
And the reason to let Claude make worse code than a professional would by hand is basically suppressed demand. Since programmers are expensive, previously code mostly got written when a large number of dollars were on the line, or when an individual programmer did something not economically optimum (e.g., hobby project).
That left a whole lot of somewhat less valuable software unwritten. It's the economic space that no-code tools have been nibbling on for years. One way to think of things like Claude Code is as effectively no-code tools. Pre-LLM no-code tools would produce data structures that got executed by special environments without ever being seen or tuned by a human. Claude Code can be used just like that, with text as the input and python as the intermediate representation that nobody ever looks at.
That approach probably isn't sustainable for what we professional programmers would call a serious project. Claude can easily get in over its head and I expect that its code decays over time, in a fashion similar to how many human teams get in a state where they just have to rewrite everything. But faster, I'd expect.
But there are a lot of unserious projects that previously would have never been created. E.g., a quick app to manage your little league team, or a bit of in-house business stuff in the "a little hard to do with a spreadsheet" range.