Chromium has a shiny appearance. It does not corrode easily as it is not very reactive with oxygen , resists scratches. However, chromium is expensive and it may not be economical to make the whole object out of chromium. So the object is made from a cheaper metal and only a coating of chromium over it is deposited.
Steel corrodes easily. Chromium does not .It protects it and gives it a better appearance. Thats why chromium is much preferred for coating on steel objects.