>>212552740 (OP)Iron rusts and also requires a vastly higher temperature to reach melting points than these guys can accidentally produce. Discoveries happened in spots where the initial resource, like copper, was readily available and later shit was the consequence of the initial tech spreading and becoming commonplace. Copper can have iron impurities, which pushes smelters to up the temperatures as they try to get rid of the shit from their target product.
Iron was so inconvenient, it actually took a whole Brone Age Collapse to make a full switch in West Eurasia, just because the long-distance tin trade routes from Afghanistan, Altai, Britain etc collapsed.