Editing is not rewriting. The edited text is not (should not be) the text the editor would have written, if the editor had been commissioned to write the copy instead of the author. It is the text the author would have written, if the author had been perfectly well informed and perfectly skilled. In some ways, therefore, editing is harder than writing.
If you don’t mind bad language, you will be amused by Giles Coren’s tirade on this subject.