Iron is stupidly abundant. That's awesome because steel is super fucking useful for boring hard duties like construction and tool making and basically all steel is majority iron by mass. It's also reasonably safe and easy to extract in a moderately pure form with modern techniques unlike other super abundant elements like silicon. There are special steel formulations that can be wildly expensive, but there's a handful that are dirt cheap because they're easy to make and widely useful.

Copper isn't like, rare, but it's no iron. It's also often mixed up with other stuff that makes copper mines ecological and health nightmares (at least here in the us). It's also become rapidly more and more in demand as the world is shifting towards replacing fossil fuels with electricity, causing higher demand for more and more copper for wiring and motors.

For real though iron is just crazy abundant