I didn't know until college that people don't usually wash their hair every day. That was such a foreign concept to me. My hair is so greasy that, unless I know I'm staying home all day, I have to wash it daily. It's also why I shower in the morning. Even if I were to wash it at night, I'd wake up with it greasy. I was flabbergasted when my roommates were talking about "hair wash days"- isnt that every day??