Because the lapiz rank isn't verry expensive and the Emerald+ ranks don't have a lot perks.To everyone saying it should be for Obsidian, Emerald+ or Diamond+:
Why? Why can't Lapiz have it?
Iron rank introduces the ability to choose maps, so it'd make sense that Lapiz gets the ability to request maps.
I'm not saying that it's wrong to think so, but you should at least give a reason to why it should be like that.