@kanade_alter I always assume it's because they're in a medieval world, thus there's not nearly enough resources to devote for research into something that seems to not be worth it. The few people who do want to devote their time to researching it likely don't have the necessary knowledge, or funds, to do so. Don't underestimate what the ability to mass produce books has done for technology.
I uhh... I was not expecting boobs to sudden materialize... I thought the cheat plate was just for protection but... it was there to act as a flood gate.