What common patterns have you noticed in traditional clothing of different ethnicities?

Okay I feel so stupid, I only just realized feminine people wear scarves over their heads because it's hot where their place of origin is. I knew that about religious people, but I didnt know why women in India and parts of Africa do. Someone please help me spot other common patterns in terms of clothing. Even culture in general, like some desert cultures discouraging eating shellfish because it spoils too easily in the heat.