How do you think those labor laws got on the books in the first place? Because labor activists advocated for them on behalf of workers. Many if not most of these activists were also pro-union/belonged to unions. If there's no pressure to keep those laws up to date, their protections will be repealed or weakened as time goes by. Unions are an important part of keeping up such pressure.And the labor laws we have on the books here make them relics of a time long gone.