Nickle provides a warmer color than chromium. So using it today is generally an aesthetic choice of the manufacturer. It is also softer than then chromium. You can create the brushed-nickel appearance, while it is difficult and economically not feasible to create a brushed chrome finish.

Prior to WW2 in Europe, components were were routinely chrome plated but the high-end frames were typically nickel plated. Some have speculated needing chrome for the war effort. Others have pointed to cost. I don't know the answer.