Pop music is usually full of lyrics that appeal to young people that haven't had the chance to experience the world much, so the obscenities such as sex and money usually appeal to them. They are also usually fast paced and great for dancing which is not something that older audiences can do as much as the young ones. Many pop songs also emphasize youth as the greatest virtue, so it's not really adequate for an 80 year old person to behave like a 16 year old and sing how great it is to be young.
