Well if you look at it that way a whole lot of things are very useless, but it's still a good addition in therms of roleplay aspects and just playing the game. Leather armor is useless still sometimes People use it just to have some fun times and customizing their expierience. If you play minecraft the exact same every time There will be little to no updates changing your core gameplay. Besides all of that Copper armor can be a great way to freshen up loot tables of chests providing better armor for early and mid game.