First, we have to realize that there is no objective way to determine what celebrities symbolize and whether they have any value. This is a matter of educated conjecture. That said, it seems that celebrities tend to symbolize at least two different things for us. They represent what we want to be and they represent what we do not want to be.
Sometimes, celebrities embody our hopes and dreams. Through them, we live vicariously. In the United States, we want to be rich and we want people to pay attention to us. We want to be beautiful or smart or athletic or all of the above. Some people get to be celebrities because they have one or more of these characteristics. We then pay attention to them because they give us something to aspire to. They also help to represent for us the things that we think we should be like.
On the other hand, celebrities are not always so admirable. Sometimes, we watch celebrities so that we can see them making a horrible mess of their lives. This allows us to feel good about ourselves. As we watch someone who has all the advantages of stardom make terrible decisions and even endanger their entire livelihoods, we can feel superior. We can tell ourselves that we are better than those people even if they are rich and famous. This helps us to feel good about ourselves and our lives.
Thus, celebrities can be important to us for what they symbolize.