BSD-style init scripts are used in Slackware and Crux. init reads the /etc/rc.d/rc.S script and takes further actions based on runlevels defined by other scripts in /etc/rc.d/.
rc.K is run in single-user mode, rc.M in multi-user mode, rc.6 reboots, and rc.0 is the only symlink in the process, being a different invocation of rc.6 that halts the system. If the non-default graphical boot of runlevel 4 is chosen, rc.4 will be read. These scripts check for the executable existence of a few other rc.foo files and lastly hand it off to /etc/rc.d/rc.local, where local setup commands are placed. Enabling or disabling services is handled via commenting, uncommenting, or otherwise editing the relevant commands in the script or chmod's of the scripts.
As there is no keeping up with dozens or hundreds of numbered and sequenced repetitive symlinks in several subdirectories, many users find it simpler and more efficient but the majority of distros use the SysV style and many of their users find it superior.