systemd fornece a compatibilidade com os scripts tradicionais de inicialização.
Para citar Compatibilidade com o SysV :
systemd provides a fair degree of compatibility with the behavior exposed by the SysV init system as implemented by many distributions. Compatibility is provided both for the user experience and the SysV scripting APIs. However, there are some areas where compatibility is limited due to technical reasons or design decisions of systemd and the distributions.
Portanto, a resposta à sua pergunta seria: "Quando a compatibilidade com o SysV é removida do systemd ."
Mas observe que o documento também diz:
Note that there are some areas where systemd currently provides a certain amount of compatibility where we expect this compatibility to be removed eventually.