Even if djb's /service claims makes sense, it still doesn't support the significantly expanded scope of, say, systemd. I mean, hijacking system logging? What could possibly justify doing that in an init system?
DBJ's /service also hijacks logging. In fact, every decent init system hijacks logging -- you want your init to daemonize processes, and when you daemonize a processes you want its stdout to get logged properly.
People didn't use inittab or /etc/ttys because telling programmers to edit these files was error prone and if they got it wrong, the system wouldn't boot up correctly.
init.d didn't have that problem, but programmers so frequently and regularly and consistently got "init.d" wrong in some other way (supervision, logging, etc) that some time in the last fifteen years most unix sysadmins stopped expecting programmers to daemonize and write pid files and simply started monitoring their services for them with tools like daemontools.