It's because when you use the native Python packaging tools, you can install a Python "wheel" into an arbitrary Python environment.

If you get Deno from the system package manager, or from deno.com directly, you're more constrained. Rather, it seems that you can set an environment variable to control where the Deno home page installer will install, but then you still need to make your Python program aware of that path.

Whereas a native Python package can (and does, in this case, and also e.g. in the case of `uv`) provide a shim that can be imported from Python and which tells your program what the path is. So even though the runtime doesn't itself have a Python API, it can be used more readily from a Python program that depends on it.