Alright, so, this is something of a follow up to an earlier thread about variety... But this time, it's less about aesthetics, and more about the building blocks of everything. Materials. I'm mostly going to talk metals here, but the same applies for everything else... Wood, Leathers, Cloth, Gemstones...
Now, this has come up a few times in various thread. 'Get rid of glass armour, it's silly' or 'Corundrum is a gem' or 'Malachite is a copper-ore'. That isn't really the problem. Orichalcum is generally regarded as being Bronze or Brass, Adamantium is a debasemant of the word for diamonds, and TES contains both Silver and Argentum as separate metals. The materials found in a fantasy are subject to the particulars of the setting, not bound by their real-world inspirations.
But here's the problem... In the real world, we have typically used 2 metals as a basis for most of our useful items. Copper, and Iron. From industrial tools to military, these the overwhelming majority of human tools have been alloys of these two metals. It's become broader in the modern world, and there have always been some variabilities in regards to value items (gold and silver, mostly) but these two, particularly ferric metals, have dominated 'useful' production for 10,000 years.
There's a reason for this. Iron based materials in particular maintain favourable qualities while being relatively easy to work with. There's a lot of detailed metallurgicial reasons why Ferric alloys almost unilaterally replaced Copper alloys, but the end of the day the point is... Metals have particular qualities which make them useful for particular tools. You wouldn't make a weapon out of Tin, nor would you make one out of Titanium (It just can't reliably hold an edge).
Now, with TES, and many fantasy settings, there are a bunch more materials that are commonly used, usually superior to any real-world counterparts. TES alone has 30 separate metals (or materials used like a metal, such as Stahlrim and Chittin) which have been used to make weapons and armour. For the most part, this has been part of a generally linear progression scale and linked to specific aesthetics, but the mechanics aren't really the point...
How do you deal with that many material options? Is Mithril just flat out better than Steel, or should there be more range and variability? This issue extends the same to anything else, such as cloth (there are 11 types i am aware of) and Leather (only 5, really...).
Are materials really that important? Are they important enough to have more depth? Or are they superficial enough to just remain style indicators?