> I don't understand why someone would willingly share their code on github where it is publicly available just to complain when others make use of that knowledge.

People like you should understand that publicly available code doesn't mean "do whatever you want" code.

The majority of publicly available code hosted on Github as a license that tells you what you can and what you cannot do with that code.

If someone uses this code without respecting the license, authors have the right to complain and even legally enforce the license if they want.

Now, you should know that there's nothing "cool" to take other people's work without permission.