That was actually fairly uncommon for most of the middle ages. From the collapse of the western empire until the military reforms c1500, standing armies were few and far between. Peasants could be drafted to fight by their lords, but time in military service was the exception rather than the rule.
It works for now, but the reason most wires have a rubber-like insulator around them is that it takes very little to Crack or abrade a thin coating such as this and turn it into a fire hazard.
I’m surprised a product with such a small safety margin is allowed for sale.