The use of the word “fuck” in The 300: Rise of an Empire

Modern films tend to use modern language. In the same way they don't do the film in ancient Greek (which would be correct) as the way they spoke is different to modern speech patterns, so would make the film more difficult to understand for audiences, especially as it's a fantasy war film.

Some film-makers do try and keep things more authentic (Mel Gibson's Apocalypto in Mayan springs to mind), but that tends to limit the potential at the box office. Most English speaking audiences will favour an English remake over the original in a foreign language, even if the remake is dire.