10 years ago, GitHub had a far better reputation and the Rust ecosystem was much smaller and less load-bearing, so "what if someone doesn't have a GitHub account" was a theoretical concern for most people. So the issue was a low-priority backlog item that everyone agreed would be nice-to-have but there weren't enough people willing to volunteer their time to it over more important and more impactful work.

Obviously, the situation has changed in recent years, so it's now considered a much higher priority by many people and some of them are actively working on it. But it's a lot of work to be done by volunteers, so it takes time.

That's the reality of open-source projects: things get done when they are important enough to motivate someone to either fund it or work on in their free time, not according to idyllic roadmaps and schedules.