[asavah]

Isn't that a fault at OS level?

Nope, this is documented.

https://wiki.debian.org/Python (same applies to ubuntu as ubuntu inherits most of debian's advantages and flaws )

NOTE: Debian testing (bullseye) has removed the "python" package and the '/usr/bin/python' symlink due to the deprecation of Python 2. No packaged scripts should depend on the existence of '/usr/bin/python': if they do, that is a bug that should be reported to Debian. You can use the 'python-is-python3' or 'python-is-python2' packages to restore an appropriate '/usr/bin/python' symlink for third-party or legacy scripts. 

Edit: In the case of kodi-send I totally agree that the best way to fix it would be to simply change the shebang locally.