This makes it easier for people to clean up their code before letting the world see it. I wouldn't be surprised if it made some people more willing to contribute.

I expect that if a significant portion of work was done to an existing fork, or a significant bug found, it would be celebrated and immediately pushed back to the community. It would be exactly the same as if I downloaded Linux, made some awesome changes then sat on it and just shared it with my friends. A ridiculous thought.

They're learning together and need collaboration tools.

Your statement doesn't make any sense given the context nor add to the argument.