Klingons are traditionally a standin in Star Trek for the Red Scare (60s era caricature of communism). What you have to understand is that the cold war of the era was simultaneously a display of might, but also fraught with spycraft. The Klingons had to represent both of these fears. You couldn't see what was happening on the other side of the iron curtain (cloaked).

Practically, they later created the technobabble rule that you had to drop your cloak to fire. That somewhat squares the circle regarding honourable combat, while still allowing Klingons to scheme.