Aluminum Wiring was normal to use in house built between 1966 to 1974. Nowadays, Aluminum wiring is wildly use in commercial & industrial.
Even though Aluminum wiring is still in used today for Electrical distributor contractor for supply service cable in residential but it is not common to use inside the house wiring system for safety concern. If the connection of Aluminum wiring is not professionally done it can be dangerous and creates a fire. I am sure everybody knows electrical circuits heat up and cool down during the normal loading. Aluminum wire will expand and shrink almost 3 times more compare to copper wire. That expands and contrast will make the connection point loose so create air gap. Eventually aluminum wire will oxidize in the connection point and in some point it spark which will lead to a fire.
Of curse, there is no safety concern if proper connection and termination are made according to CEC ( Canadian Electrical Code) by a qualify person.