Why do subcultures stress violence?

Some subcultures use violence and fear to maintain authority and order. In a simplistic society - which they are - physical strength indicates the ability to lead intelligently (a common strangeness in most parts of the world). The violence may also distract the hotter heads in the group from actually thinking themselves, and so "elders" or more senior ranked members may promote it amongst them to prevent subversiveness and discontent in the lower ranks.