Re: backup-buffer-copy loops if old backup can't be deleted

[martin rudalics]

>      (while (condition-case ()
>                 (progn
> !                 ;; Failure to delete an existing file is an error.
> !                 (if (file-exists-p to-name)
> !                     (delete-file to-name))
>                   (copy-file from-name to-name nil t)
>                   nil)
>               (file-already-exists t))
>        ;; The file was somehow created by someone else between
>        ;; `delete-file' and `copy-file', so let's try again.
> +      ;; FIXME does that every actually happen in practice?
> +      ;; This is a potential infloop, which seems bad...
>        nil))

I'm too silly to understand this.  Why can't we use

(copy-file from-name to-name t t)

here as in Emacs 21?  What was the rationale for this loop?