Whether a party really needs an attorney depends on the facts of the case. Attorneys are professionals and know their field extremely well. They can offer you their expertise and counsel you through your divorce.
Divorce lawyers can also see issues that may not occur to couples proceeding pro se, such as tax treatment of financial issues surrounding the divorce, issues with exercising possession and access of your children, and even discovery of hidden assets. A good analogy is if you had no medical experience, would you treat your own broken leg or would you go to a doctor to have it repaired?