Don't they have some kind of small scale force field technology that stops anything (eg. bullets) moving above a certain speed? iirc there was a duel where Paul Atreides was consistently a tiny bit slow on his attacks, due to his training in aristocratic duelling where everyone has personal shields, which was interpreted as him deliberately toying with his opponent.

For bonus points, energy weapons weren't really used because if one hit a shield, it would cause an explosion (centered on the energy weapon maybe?) that would take out half a city.