I don't know if there's an official reason, but my guess is that it's slightly out of scope for pip: pip is a packaging installation tool, not a virtual environment managing system.

uv, being both, is a more natural fit for an implementation of that PEP.

Here's a relevant discussion: https://discuss.python.org/t/idea-introduce-standardize-proj...

It's completely out of scope for pip, which is purely about modifying the set of packages installed into non-transient environments.

Pipx is a wrapper that does more or less what you're looking for (including PEP 723 support), but it arbitrarily refuses to process top-level packages unless they specify an entry point (which makes them "applications" even with abstract dependencies).

I'm planning to support it in PAPER, which can roughly be described as my vision of what pip and pipx, taken together, should have been.