Most people assume that a white wedding dress symbolizes purity and virginity. So in today's standards, that's what it means. If that's why you want a white wedding dress, all the power to you.
But did you know that the white wedding dress was never intended to be a symbol of abstinence before marriage? Originally the wedding dress was simply the best dress a woman owned, often her best dress was an heirloom from her mother because fancy clothes were super expensive. In fact, white fabric was THE most expensive fabric around because of how hard it was to get a true, perfect white fabric. So the uber rich noble women could afford a white dress, it was a symbol of her status. It showed the witnesses of the wedding that here was a woman from a wealthy family.
Less rich families could eventually buy the fabric and make their own (often using discarded dresses from nobles and cutting them down into simpler styles), and then passing on the dress to their daughters because it was so special. This is why there is that tradition in some cultures/families to have all the women wear the same dress when they get married. It's accumulated emotional worth.
Now there are a lot of cultures that do not use white for a wedding dress. It's actually considered a bad colour to wear because they use it at funerals. A white dress is very much a Western European/North American symbol.
