Culture is about power dynamics, unspoken priorities and beliefs, mythologies, conflicts, enforcement of social norms, creation of in/out groups and distribution of wealth and control inside companies. Culture is usually ugly. It is as much about the inevitable brokenness and dysfunction of teams as it is about their accomplishments. Culture is exceedingly difficult to talk about honestly.
Read the full post, which is about startup culture, but I thought this paragraph was very insightful and applicable across organization types.