Yeah totally. Pretty much every time I have a code idea, I create a new github repo. If someone went through and did pull requests on every single one of those to add a license, it would probably do nothing but piss me off and convince me to spend time figuring out how to report the account. That being said if an actual individual developer sent me a pull request/email/tweet/whatever asking for a license, I can promise you I'd be sitting there on my phone scrambling to get a license on there.

If GitHub wanted all the repos on GitHub to have licenses, they would require it, or create a policy where all repos with no licenses automatically meet a minimum licensing requirement.