> If you have a large amount of Python 2 code that doesn't make sense to rewrite as Python 3 but does make sense to keep developing as opposed to just keep running as-is, it makes sense to want compatibility-preserving improvements to the language.

But it really doesn't. If the new features are that valuable, you can convert your code. It's not actually that hard (I have a few 100kloc ported forward now, with millions of lines of dependencies that says so).