Wisdom teeth have a purpose. They are another set of molars, but more often than not they cause more problems than they are worth. Wisdom teeth can come in misaligned, facing any direction. They can even try to come in horizontally, growing into your other teeth. This can damage your nerves and even your jawbone.
Since wisdom teeth are often harmful, most dentists recommend their removal. The surgery goes much better if you get the teeth removed before any signs of problem. The recovery is easier also. Surgery and recovery are also easier when you are younger.