Still I don't understand why is it the default license that people instead of public domain e.g. BSD0. Sometimes it's not obvious how to satisfy the attributio

Still I don't understand why is it the default license that people instead of public domain e.g. BSD0. Sometimes it's not obvious how to satisfy the attribution requirement for example when I am taking only a piece of code like a single function that would later dissolve in code of my project. I am not thinking about that when I am copying the code from a public domain project. Why do you think that requiring attribution for your code is important?