For the most part of their history, such societies were habitually entangled in raids, counter raids and conspiracies. Returning home to a heroic welcome and ululating women after pillaging another village was very appealing to the machos of those days and it made the young yearn for more war and raids to satiate their egos. That was an accepted way of life in ancient times. Trying to preserve such cultures and attitudes in modern times, when people have better things to do instead, is immoral and stupid. The mentality of the middle-ages is just not fit for today.
Leaders come out from within societies and reflect the psyche of their societies.
A worrier society breeds worrier leaders. A peaceful society breeds peaceful leaders. When a society does, it is easy to tell. Mature societies are those who have developed enough to appreciate the blessing of peace and stability. The aggressive and warlike individuals among such societies are a minority who are considered an outcast.