They can't support reading the poetry data because it's not generic. Nor are most practical implementations of tools using pyproject.toml because they all use custom tool-namespaced fields in pyproject.toml: it's far from a standardized format yet, despite the push for using it from the people that made it.

I still wish poetry would support setup.cfg in parallel. It has been working for 2 years, is compatible with pip, setuptools and the whole legacy stack, and most fields are standards and documented.