Soap reacts differently in hard water. A lot of people with super short hair (IE buzzed on a 1 or 2 guard) just use soap. It works fine for most people in this case (note that buzzed heads are generally less prone to being dry anyways). With longer hair, I've heard it dries the scalp/hair, but have no idea if it's actually true (or if it would necessarily affect everyone).
With hard water, however, soap will turn your head into a shitstorm of scum.
Anyways, I do hear what you're saying Ren. When I was younger, I used to go on 2-3 week hiking/kayaking expeditions and often wouldn't bring shampoo. Your hair was getting wet every day and you bathed, which was enough when there's only like 13 other dudes around you for weeks on end. I don't remember my hair being bad past the initial phase where you could tell it was greasy.
But cutting shampoo out in the city? I personally wouldn't do it. Hair is like a smell sponge (or at least that's what everyone says). Shampoo negates that a bit....I think.
