Having a bald head, I were hats in extreme weather. In the summer I wear them sometimes to protect my head, not from sunburn since I don't burn, just from overexposure. I live in Oregon so in the winter it rains mostly. I wear hats sometimes to keep my head dry. If it is really cold out, I'll wear a hat to help me keep warm.
There is a variety of hat styles in my closet. I don't own a traditional baseball cap. Almost all my hats are casual, since I don't have much need to dress up.