I can't speak for other devs contributing to the project, but I think the mailing list is a great way to do this. Ultimately, what you want is a simple way to track information about reported issues, discuss the details, make it reasonably simple to search for existing issues, and post patches fixing the issue. A mailing list does all of that, without having to deploy (and maintain and curate) a separate system.
Why do you think it's more difficult to report a bug this way, compared to a bug tracker? There's even a "report a bug" link on the project home page, where you can submit a bug report through a simple web form (you need a community account, but every other bug tracker I'm aware of requires that too).
Can you explain why you think a mailing list is less efficient than a bug tracker?