We could come up with similar (yet not completely identical) materials of our own. It's a world where we have 70-foot chickens, giant squid and trees with a tendency to kill dragons. Why would it have similar minerals? Could we make a metal that functions as an aquifer before being mined? Or does the aquifer mining exploit not leave boulders?
Real life has giant squids, you know. And our mod lacks 70-foot chickens.
Also, this mod has had Iridium and Meteoric Iron from near the beginning. Both of which are real-world materials, though because we lack other metals, they appear almost everywhere as tools and weapons, despite the rocks they're mined from being relatively rare. I posted a lengthy rant about why our make no sense a while back, but to sum up "Why would the natives even call if meteoric iron if it forms so much of the planet that it would be impossible to tell that it came from meteors?"
And; " 'Draw Iridium, villain!' just doesn't sound as good as 'Draw steel, villain!' "
And there's no reason we can't have mundane metals and fantastic metals at the same time: In fact, we MUST. When ONLY fantastic metals exist, people have no point of comparison. "Stronger than steel" tells me something about the metal; "Stronger than Lunalium" tells me nothing, because that's just more jargon. "Gold" brings to mind riches. "Selenite" does not, unless I know it's "almost as valuable as gold" or "twice as valuable as platinum", etc.
You may as well ask "Why does our world need boring old lances and clubs? People should wield Asjhajksdf's and Tierioyeir's!"
Take halflings for a good example. We know they're about half the size of humans, and so they provide a good point of comparison that let's us visualize the size of the other creatures of the world.