Aluminum alloys have widely replaced steel in military equipment because they provide the same protection and are lighter. But an armored vehicle made of aluminum alloy costs twice as much as a armored vehicle made of steel. 
from a financial point of view, it is not advisable to replace the armored vehicles made of steel with armored vehicles made of aluminum alloy with the same protective performance.
The maintenance cost of the armored vehicles made of steel is the lowest among all kinds of armored vehicles currently used by the army.