If I understand correctly, the main goal here can be summarized in the quote below: "The motivation: modeling Docker containers as regular processes [...] we

If I understand correctly, the main goal here can be summarized in the quote below: "The motivation: modeling Docker containers as regular processes [...] we want processes to behave just as if they weren’t running inside a container. That means handling user input, responding the same way to signals, and dying when we expect them to. In particular, when we signal the docker run command, we want that same signal to be received by the process inside." and that seems to me as the core reason why they can't just use a simple init system (like e.g. runit I suppose?)