Sure you can have high standards for contributors. But if said contributor can't be bothered to cleanup his patch for upstream submission, then the absence of G

Sure you can have high standards for contributors. But if said contributor can't be bothered to cleanup his patch for upstream submission, then the absence of Github won't encourage him to suddenly cleanup his patch. He'd most likely keep his changes private. Remember, people are lazy and not going through the whole cleanup/submission route is definitely easier. With Github at the very least you can see that those people exist and what they've been up to. To me this is still better than the alternative.