I know people who refuse to use async_trait for documentation reasons alone. The macro-based solutions aren't always pleasant to use and often come with a lot of weird tradeoffs. And yeah, I agree that most users don't need to write theme explicitly--I'm arguing that users are currently significantly impacted by the lack of them, even if they are never in a position where they'd consider writing them themselves, because it prevents library authors from writing precise APIs. For example, you might not be wanting to write GATs like the Hyper authors, but anyone using Hyper for anything nontrivial (and that's surprisingly common, IME) is certainly negatively impacted by the massive complexity caused by needing to work around their absence.