I learned to love uv because of this usecase but I still find it against the Zen of Python that an official (and, dare I say, extremely useful!) PEP is not supported by the official Python tools.
This is the first time that Python didn't come with "batteries included" from my POV.
Now I also have two Python dependency managers in my system. I know there are volumes to talk about Python dependency management but all these years, as long as a project had a requirements.txt, I managed to stick to vanilla pip+venv.
That's been a bit of a trend for the Python build specs. Pretty sure the pyproject toml predates the tomllib library. So for a few versions you had to specify your module in a language that Python couldn't read natively.
Which is worse than just having a default way for including metadata that's not used. That's what makes it metadata after all. Otherwise it would just be Python syntax