Good reply, but one nitpick:

It’s also reasonably safe and easy to extract in a moderately pure form with modern techniques unlike other super abundant elements like silicon.

Silicon smelting is arguably easier. If you have excess quartzite in your furnace it won't form silicon carbide, while steelmaking involves being really careful to not get too much or too little carbon in the melt. Silicon becomes expensive for electronics because the industry wants 99.9999% purity absolute minimum. What comes out of the arc furnace isn't read except for use in other metallurgy.

I'd also like to point out other elements can do the same basic all-around-skookum-alloy job as iron, like nickel or titanium. It's just that none of them are everywhere.