When do we not need to acknowledge our sins? Well, according to the 2002 Missal at weddings. Wouldn't want to make such a happy time a downer by recognizing our sinfulness and need for forgiveness. Can't have it on Ash Wednesday either. After all, we already do the ash thing, we don't want people to feel bad about themselves do we? Or funerals, can't have a penitential act at funerals. People might start thinking about sin and next think you know they will start praying for the dead instead of celebrating their lives.
Seriously, one of the great faults of the modern age in the lack of a sense of sin. Do wedding parties not sin? Do brides and grooms not need to kneel before God and ask for his forgiveness before they receive the awesome sacrament which makes them an icon of the love between Christ and His Church?