Isn't there a requirement to acknowledge the original author for all copyrighted work, no matter how permissive the license is? That is, the only way to not make it a requirement is to put the work in the public domain, and in some countries, it is not even an option.

That is, how can you know who the copyright holder is if you don't do that?

Considering that not all projects are littered with (c) Stack Overflow User, I may have the wrong idea, but it is definitely something I have seen somewhere. I am not a lawyer, obviously.