Is is perhaps because the other init systems are only willing to touch a very narrow definition of init while depending on rotten, unmaintained pieces of the ecosystem like consolekit without being able/willing to maintain it themselves?
Or perhaps the plan is to let systemd folks do that while shitting on it so we can cook up a 600 LoC 'minimal init' while outsourcing a whole lot to systemd maintainers while taunting our minimalism?