Why?
Giving away the bride dates back to when women literally belonged to their father. On marriage she was given with her property to the groom who took over from the father.
The groom standing on the right is thought to stem from when a groom used to kidnap his bride. If he then has to fight off other suitors, he would hold her with his left arm and keep his swoard arm free.
Seating Families on opposite sides of the church stems from the days when daughters were offered in marriage to unite opposed tribes, in order to avoid fighting in church.
The ritual of throwing confetti originated in Italy where rice and nuts were thrown at the bride to bestow prosperity and fertility to the couple.