because the various legal systems regarding copyright are a abomination, that simply do not allow me legally to waive my rights.
CC0 claims to waive my rights to the fullest extend, but reserves my right to file a patent. Not what I want.
The closest seems the unlicence:
https://directory.fsf.org/wiki/License:Unlicense
(but it seems not recommended by GNU, for whatever reason - they recommend the CC0 instead)
https://www.gnu.org/licenses/license-list.en.html#Unlicense
This is annoying because I just want to make it clear and simple for anyone without doubt, that my project shall be free for any use, any time. A layperson cannot divide between all the various GPL, LGPL, MIT, etc.
So unlicence is my current favorite, until I find the caveat.