Why does Error::downcast<E> and Error::is<E> require E: Debug

You can use a type which only implements Display as context for an Error. But then you cant take that Error and downcast it to that type. The downcast\, downcast_ref\, downcast_mut\ and is\ have a requirement that E: Debug but I dont see a reason why it would be needed.

Here is an example:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=f862ec4d05048736f45741370f192680