One innate reason that make media always reflect the value of current society is, their authors come from the current society, who are already deeply affected by the value around them. One example is what people like and feel in different times reflect in the music. 100 years ago, when more people live in the countries, life is more peaceful, and people more like quiet and simple life, country music are popular. At time that, the lyric of the country music reflect the peaceful and simple life people enjoy. But nowadays, in our modern life, more and more people live in modern city, crowded, noisy and stressful, which make people more easily feel angry and yearn for release. So today’s pop music, reflecting our modern life, are more dynamic and quick, and most of them more noisy. Some lyric of the pop music will describe a people crying for his/her dissatisfaction and pressure from the society.
Another good example that media reflect value of society is how people in different areas treat sex that affects their media. In some religious countries, people consider sex as a taboo. People tend to not talk about it in public. So it is not easy to see authors describe sex explicitly in their works, no mention that public media will advertize this topic. But in western countries, sex for their people, is just a common and regular need in their value, so it is common to see that the medias come from western countries will even describe sex.
Simply to say, books, music and all kinds of different works and value