Why does sysvinit force the console to be its controlling terminal for any wait-type subprocess?

Question

I'm reading the source code init.c of sysvinit(now replaced by Systemd), in the function spawn()(where init creates subprocesses), there is a comment at line 1165:

    /*
     *  In sysinit, boot, bootwait or single user mode:
     *  for any wait-type subprocess we _force_ the console
     *  to be its controlling tty.
     */

But I'm still not understand it. Could anyone explains the reason in more detail?