system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Why don't most Sith/Jedi wear lightsaber proof armour? There are materials resistant to it so I don't see why they don't just make armour out of it.
gpt
Lightsaber battles basically don't happen. So it's never been necessary. 

For the previous thousand years of history, the Jedi thought they were alone in being saber-wielding force-using warrior monks. There were other force traditions in the galaxy, but none nearly as large, and none with the exact traditions of lightsaber building and combat. It's really on the Sith that use lightsabers in opposition to the Jedi. And really, it's only to spite them. Bleeding a Jedi's crystal and using the power against them is just one tactic among many the Sith used against their eternal enemies. Even moreso after Darth Bane reforged the entire Sith order into an entity that seeked revenge. 

And sure, Jedi sparred with one another all the time. And a few standouts were absolute masters of combat, either from their natural talents or years of practice. But for the most part, Jedi used their lightsabers in what was basically advanced meditation routines, physical fitness classes, and basic self defense. Nothing that required anything more than normal clothing. 

And on top of that, don't forget that Jedi can see the future. So they frequently react to attacks before they happen. When fighting pirates or smugglers in routine actions for the Republic, or later against legions of battle droids, even the most novice Jedi could be an overwhelming opponent. And in the rare events that Jedi and Sith locked blades, both sides were simultaneously striking and reacting to things that had not yet happened. Which would make any sort of armor functionally useless.