Because they don’t want their repo cluttered with PR branches. It’s maybe not obvious, but in a public project anyone could branch and submit a PR which leads t

Because they don’t want their repo cluttered with PR branches. It’s maybe not obvious, but in a public project anyone could branch and submit a PR which leads to a mess. This is how it’s done in many large companies as well, not just OSS. It saves you from scratching your head wondering if deleting this year old feature branch is actually throwing good work out. The news is that this person is working on the project, this clone is evidence of that.