Why is a home-rolled cd script interesting when there are many more mature, feature-rich cd-tools out there?

* http://www.skamphausen.de/cgi-bin/ska/CDargs

* http://micans.org/apparix/

* http://github.com/joelthelion/autojump

* http://github.com/rupa/z

* http://github.com/flavio/jump

Also, the title is misleading. I thought it was actually a commandline tool that removed the need to cd most of the time, like lightning: http://tagaholic.me/2010/04/08/lightning-speed-for-your-shel...