The vein in the ring finger is connected to your heart.. And your husband is your heart which you can live without =D
According to tradition, the wedding ring is worn on the left ring finger because the vein in the left ring finger, referred to as the 'vena amoris' was believed to be directly connected to the heart, a symbol of love.
Because it looks good in it. Or because it is your second step to enter in new world where you have your Husband. First step is with your family.