Back when the primary (if only) pathway to sainthood was martyrdom, this day for commemorating and honoring all of the anonymous martyrs of history, those who died in groups or whose identities were not known. As time passed, and the nature of sainthood changed, the day has come to honor all the saints. Among Protestants who observe the liturgical calendar, "saints" is considered in its New Testament usage, meaning all believers. They have thus reinterpreted the feast of All Saints as a celebration of the unity of the entire Church.
Whatever take one has on Sainthood and the Feast of All Saints, it is a day to honor those who have gone before us, those examples of the faith who have demonstrated heroic virtue.