We did.

BHP had massive steelworks in Newcastle and Wollongong (~150KM north and south of Sydney), aside from others.

BHP found it was cheaper to do it in other countries where environmental, safety and labour laws weren't such as hassle to deal with (aka: Paying a living wage, avoid killing your workers, and limiting the impact you had on the surrounding population).

Newcastle also had a massive Aluminium smelter - but again, cheaper to do it overseas.

It's a repeating pattern.

Alcoa is the largest employer in South Australia, and operates the world's largest integrated bauxite mining and aluminium refinery.