Even if you look at Kitware own products they full of quite outdated and ugly code. I think it's because amount of code and platform-specific hacks in CMake / CPack / CTest is just too hard to maintain and many things will break hard while there was no changes in them for years.

Also copy-pasting sometimes work better simply because very few developers actually able to check how their own configuration work across multiple platforms and endless number of Linux distributions. It's might look easy to make your own configuration, but once you try to at least cover Windows, Mac and Deb-based Linux it's take weeks to debug everything. Instead you can copy-paste someone else module, change few lines and it's will already cover everything you need.

EDIT: typo: on -> once