Its revolutionary ideals no longer had any place . As a result people began to look inward . The music became far more introspective ( it is interesting to note that metal music went through a similar change , albeit about a decade later ) . Ones personal experiences and the way in which one was affected by the world , became the driving force of musical content . This introspection was to give birth to the Emo sub - genre .

Question: What may be the reason for music evolution ?
Answer: Because the people want something different .Because everything evolves and changes .Because that 's what the radio stations want .Because it changes according to popularity .