I suspect a complex WYSIWYG editor like Google Docs benefits from this feature since the selection behaviour is heavily customised (and it has to be in order to

I suspect a complex WYSIWYG editor like Google Docs benefits from this feature since the selection behaviour is heavily customised (and it has to be in order to support most of its features). The browser can't comprehend most of the things you might be selecting and copying from such a document, so it makes sense to replace the clipboard with a more accurate representation.