CWP story started as few scripts for cPanel, then all what you see on index page of CWP was added in cPanel as addon (live process monitoring, ram, disk space usage services manager ....), after that there was more than 50 modules for it....and after all of this work done why to use cPanel if custom panel can be build using all this?
Because of cpanel prices it's decided to build custom panel which would be free for everyone.
Now to question why CWP website is on cPanel ?
* simple answer, this is SSD server powered by super cache server in front which is very fast and because this is shared server we can not install cwp on it and we need VPS & Dedicated servers for developing.
CWP is now used world wide and even public country institutions are using it.