Because the game doesn't use a hit point system. there's no real reason to buy or craft upgraded weapons or armour. It would unnecessarily inflate the inventory system for something that doesn't really have an impact.
Also, Wayfarers can't use magically-enhanced gear, so most of the weapons and gear available from weaponsmiths would be ineffective. They have their Alassar steel sword and it's the only one they need to do their job.