My hair doesn't get greasy, really, my skin and hair is not oily at all. I wash my hair every second day just because I feel dirty. I shower every day, obviously, but I try to avoid wetting my hair every other day, because if I wash it too often it totally dries out my hair. My hair is probably about half-way down my back now, shortest it's been in many years. I've always worn it very long, it's sort of wavy and I don't like that it get's frizzy sometimes, so I do flat iron, sometimes, but I rarely blow dry. I've never put dye in my hair, I'm afraid of the damage, and if I ruin the colour, I can never get my natural colour back. Plus, I know people pay a lot of money to dye their hair my colour... don't want to mess it up.
I know a few black people who tell me they only wash their hair every couple of week or so, and I'm guessing because of they type and texture of the hair, it requires a different treatment and routine than ours... I can't imagine waiting more than a few days to wash my hair, I would feel disgusting. Even though it doesn't look dirty, I woud feel dirty. I can't really see how washing hair with just water would do any good at all, why bother.