You're surprised that GitHub allows people to host arbitrary repos?! Do you really prefer that GitHub would go "I'm sorry Dave, I'm afraid I can't let you do that"?
https://docs.github.com/en/repositories/managing-your-reposi...
"You're under no obligation to choose a license. However, without a license, the default copyright laws apply, meaning that you retain all rights to your source code and no one may reproduce, distribute, or create derivative works from your work."
If I'm looking at everything else on the internet with the purpose of trying to transform it in some way, that's definitely a potential copyright issue.
Your last sentence basically admits that the fundamental legal situation of code and prose, independent of usage, is the same. If your only possible interest in code is to "transform it in some way", that's your problem, not ours.
On Github I don't just want to give that permission to github, but to everyone who clones my repo.