Also even before LLMs, a lot of software was already kind of semi-disposable.

You write an app, maintain it for a few years, then once the code starts getting a bit old and messy developers start advocating for writing a new version from scratch in the latest shiny language/framework and rinse/repeat.

That was already completely normal in the 2010s before LLMs in my experience, most developers don't want to maintain other people's old code and will try and manoeuvre politically to avoid it