Marriage is a public commitment of two people often under God with witnesses.
Wedding celebrations are for celebrating to satisfy someone s ego. Sometimes the bride, sometimes the groom, sometimes the parents.
I think weddings have always served another, social purpose, of bringing the community together to witness and celebrate a union which constitutes the central unit of human society. By participating, all are partaking in a recognition of what the institution of marriage really means to the larger community.
This is very obvious in cultures where marriage is still considered an important duty that the individual has to family and society. Maybe not as obvious in the US, nowadays.