I like shampoo (gentle shampoo about once a week) and, more importantly, conditioner and styling products because I like my hair to look more organized and smooth. I've seen plenty of pictures from the past with people with my hair type and generally speaking it's bad. And mine was pretty bad before I figured out it needed conditioner left in.

I have met two people with curly hair who did water only and both had good hair, both had fine textured loose curls that were angelic and blond.

I don't think body or hair cleansing products are scams, nor are moisturizing products. Or perfumes. They all do what they say they do.

SOAP, natural soap should never be used in hair. Soap scum is no joke - soap will lock the dirt onto your hairs in a nigh-unbreakable film of soap scum if you have minerals in your water (like most of the world does). And in soft water it will strip more oil than shampoo. Never use soap on your hair. If you are really so anti-shampoo then yes, nothing but water. Just rinsing it out will do a lot. It's not "chemicals" that trigger overproduction of oil, it's the removal of oil and sebum. Soap is worse for your scalp than shampoo by every possible measure.

As far as pollutants go you may be right. I haven't considered that, just the fact that my head always felt greasy before I stopped shampooing. And you can use a soap without chemical additives every few weeks without triggering your body to go ham on oil production.