This is just a fact of how attribution works in Git. It's not GitHub's responsibility to figure out exactly who should be given credit for which commit, they're just a viewer on top of Git commits. Imagine you did some work at some workplace years ago, and you want credit for it. You don't have access to that email anymore, but you'd still like to have the credit and have it link to your account. That's the usecase.
> It's not GitHub's responsibility to figure out exactly who should be given credit for which commit, they're just a viewer on top of Git commits. If it's not GitHub's responsibility, then why are they doing it? Nobody forces GitHub to attribute commits to GitHub user accounts. (And yes, you answer this "why" question in your next sentence, I'm just pointing out that your argument is nonsensical.)
Sure, I could claim an original Unix dev's work. But what does that actually do, besides raise questions I can't answer at interviews?