IMHO there is a big difference between having total control/0 challenge and finding a creative way to work around a problem.
I personally dont understand the restriction. Maybe they want you to explore? Maybe its based on viking lore with metal properties? I dont know but the fact we have portals makes no sense to me that some things can come through and others cannot. Being able to keep all of my materials in one place doesnt remove any important gameplay from my experience It just cuts down on the drudgery of busy work which is not something I enjoy in my gaming experience.