It's that simple. Hollywood is a business. They will cater to their audience. If people don't want to see violence and sex they won't go but unfortunately people want to see it, and Hollywood will continue to make it. So, they have a right to.
Film is an art form.
An art form that is embraced by the mainstream. A new rating system is, in fact, a great idea for Hollywood. Opposite to what McCain, Gore and Bush think it will accomplish, a new rating system would cut down on censorship and allow more freedom for filmmakers. If there are more ratings to categories films, then this will allow more freedom. With the current rating system, if you want to release an adult targeted film you have really only one rating to generalizes all different types of adult films.