If Utopian ideas are not meant to be acted on, what other purposes do they serve?
Often, authors who write about utopian or dystopian societies have the purpose of hoping that their reading audience will act. Otherwise the hyperbole or exaggeration of their novels are null and void. They don't matter.
I do not believe that each one of my students who reads Brave New World or Fahrenheit 451 automatically goes out and acts upon the ideas developed throughout the story, but I do believe they do two things:
1. They learn to critically think about the world in which they live. Utopian and Dystopian novels make us think about the qualities a good and strong society should have. They make us think about the flaws too. It appears you are reading Lord of the Flies. Although children would think a life without parents should be a blast, the kids quickly come to find out (Ralph and Piggy in particular) that without mothers to nurture, fathers to protect, and police to enforce the law, anarchy will soon take root. This lawlessness resulted in many failures for the boys and it depressed and hurt them in more than one way. We should be able to look at our own boundaries (governments, police, laws, family structures, business ethics) and be thankful that at least some structure is in place because without it, people could steal, kill, and destroy.
2. They entertain through hyperbole. People like TV shows that mock society and culture. It helps us laugh at ourselves and the common mistakes we make. I enjoy watching a new TV show about a telephone center in India because we have all dealt with a telemarketer over the phone who is stationed in another country thinking that we were calling a US number. It is easy to get frustrated with the communication barrier, but it is much easier to let the tension fade and laugh at ourselves. Utopias and Dystopias make us look at our own current scenario and it seems let stressful.
Hope that helps!