Because kali-core is broken for over half a year now with dependency conflicts. I just installed a fresh kali-core template and as @arkenoi mentioned, it is a plain debian without kali repos.
I can however convert a fedora or debian to a pentest machine, which will force me to work through this weekend.
However as there is a kali-core template i expect it to work. Otherwise the template should be removed.
As this thread has 17k+ views i suspect that i am not the only one interested in a working kali template.