Copying or rather duplicating a note seems like a really useful functionality for instance when the note includes extra information such as the “source” (book+page number, URL, …) of the data. Also having many notes with the same tags is probably a common use case. Basically any field that is “sticky” while adding new notes would benefit from this feature. These “sticky” fields are fantastic, but only work if you are adding the same kinds of notes in a row, not if you are switching between different notes that for example require different source information on them.
There are several plugins that already do this and it’s also something people ask about time and again. The problem with plugins is that you have to trust the authors and they easily become out of date and need bug fixes (as is the case currently with GitHub - Arthur-Milchior/anki-copy-note: An add-on to copy anki's note and Anki 2.1.47).
Implementing this feature in Anki desktop sounds like big value / little effort, in particular because code from the plugins can possibly be re-used. As an alternative maybe it could be supported as an official plugin that is always kept up to date with new releases.