Copying older works was considered a valuable skill until very recently. Even great artists had to first learn and improve their skills. And what better way to do this than to imitate older artists?
Michelangelo started his career as a forger. He proved (and improved) his skills by making copies of roman sculptures. Similarly, Van Gogh copied works from his favorite artist, Jean-François Millet. He considered his copies “translations” – like the way a musician interprets a composer’s work.