I think it's to account for legacy behaviour. Before this option was avialable you could just use a gh-pages branch to trigger GitHub Pages to render. Anyone who creates a branch locally with the same name and pushes it up should get a Pages site automatically. Best thing to do is to branch gh-pages to a name other than this and then turn it off and delete the old branch.
What if you fork a repo with GitHub Pages and you need to keep the branch to be able to create Pull Requests?
Every time I push to my fork it sends me an EMail saying the custom domain is taken.
I tryed changing the domain for my fork but that didn't help. I can't disable it as well.
So basically I'm stuck.
Thanks for the explanation of how it's related to legacy behavior. Not being able to disable GitHub Pages when we have a `gh-pages` branch has become an annoyance for our project. Frankly, I don't understand why the "Disable GitHub Pages" options needs to be innaccessible. As long as it is opt-in, I don't see how it interferes with any legacy behavior or repositories.
There is a button to disable gh-pages, but it's greyed out. It's confusing
I understand you can by deleting the gh-pages branch, but why is that needed? There is a button to disable gh-pages, but it's greyed out. It's confusing.