conda doesn't just package python libraries, but also the C/Fortran/other bits that the scipy stack often depended on. With the rise of binary wheels that is less needed though
Fundamentally it is a fresh usr/bin per environment with all that can go into that. Not just python tooling. R packages. Binaries. All of that. Env can be exported as a yaml file and trivially shared without appending some header to all scripts you write.
I think it's more about tool X vs Y, but about ecosystems and packaging approaches; in other words Python packaging (which has tools like pip, uv or poetry) vs conda packaging (which has tools like conda itself, mamba or pixi). https://pypackaging-native.github.io/ is an excellent starting point to learn about the limitations on Python packaging for native dependencies and compiled extensions.