Diane Keaton always wore a hat primarily for protective and personal reasons. She explained that her signature style, which includes hats and high-necked clothing, was significantly influenced by her battles with skin cancer and her desire to protect her skin from the sun. She was diagnosed with basal cell carcinoma at age 21 and later faced squamous cell carcinoma, which led her to adopt sun protection measures like wearing hats, wide brims, turtlenecks, and scarves.

Beyond health concerns, Keaton also described her hats as a form of armor that helped hide flaws and insecurities, providing her with a sense of security and comfort. She admitted that her affection for hats was partly because they framed her head and also because they shielded her from anxiety and self- consciousness. Her style choices reflect her need for protection both from physical health risks and personal insecurities, making her iconic look a blend of fashion, health awareness, and emotional shielding.