Steelmaking might be considered a strategic industry.
It would not be wise to let all of the mills turn to rust. If you think dependence on foreign oil is bad, wait till you add dependence on foreign steel. If there is a war (a real war), we could be SOOL.
I'm not saying that that's what is likely to happen: I'm not qualified to do industry analysis. It is a worthwhile question to pursue, though.
Still this does seem like a political decision rather than a strategic one.