Over the past several years, I've come across a number of people online who have stopped using shampoo. What used to be the province of a tiny number of usually SCA people with very long hair seems to going more mainstream. More power to them. But they mostly seem to be using a tedious system of baking soda rinses alternated with vinegar rinses which makes me tired to think about, so I don't know why they didn't first try an easier way: just use a small amount of shampoo, applied only on the scalp. And unless your hair is very short, don't wash it every day.
Unless you've fallen in a mud puddle or have applied something like oil or a henna pack to your hair, you don't need to put shampoo on your hair. The point of "washing your hair" isn't to wash your hair, so much as to wash your scalp. Your scalp is what produces the oil. That oil, which both moisturizes the hair and can make it look dirty, has to travel down the hair; the hair isn't making new oil all down its length. This is why the longer your hair gets the more likely it is to get split ends and why people with long hair will notice their hair starts to look a little dirty or oily near the roots when most of their hair looks perfectly fine.
Applying shampoo only to the scalp is apparently a bizarre and "not true" idea to some people, even hair stylists; I once had one gush at me when she was cutting my bra-length hair off to shoulder-length, "You are going to save so much money on shampoo!" But this isn't some crazy idea I came up with on my own. In my early to mid teens I read an article in a women's magazine about two or three models who had kept their long hair, against the pressure to cut it shorter. One of these models had very lush hair. She said she washed it every three days and applied shampoo only to the scalp, then applied a conditioner to the ends only. I've used shampoo only on my scalp ever since, except for the exceptions mentioned earlier.
What's more, I use cheap shampoo, I use more of it on my scalp than the minimum needed, I wear my hair long, and beyond a handful of homemade hot oil treatments over the years (mostly cuz I was bored), I used no conditioners until recently. I don't even have one of those chlorine filtering shower heads that I used to see in Real Goods catalogue. But my hair is healthy and when I wear it loose in public I often have women stop me and say how pretty it is, although that may be largely the color (long red hair has novelty value).
Washing my hair this way about twice a week and never using conditioner let me have bra-length hair (i.e. hair that covered the bottom of my bra strap) for years without any split ends. In my mid-thirties, after a while with hair so short I didn't have to comb it, just run my fingers through it, I decided to see just how long my hair could get. Somewhere around waist-length I transitioned to washing my hair about once a week (more in summer than winter) and eventually it reached to the top of my hips. I'm forty now and it seems everything on me is falling apart or drying up, but I've discovered that if I apply conditioner to the ends occasionally, I can have waist-length or longer hair with only minimal split ends. (That's split ends I can see looking close up, not something you can see across the room, like the straw piles my sister used to get so vocal about that appear on some women's heads after a permanent.) Maybe if I spent more time on it, I would have no split ends even at hip length. But what I'm doing works well enough for me and requires only the smallest outlay of time and money.
I don't doubt the "no 'poo" folks get good results, but for me it would take more effort than what I do now. It wouldn't save me much money (an inexpensive bottle of shampoo lasts me a year or more, despite the fact I use a bit more than I strictly need), and my hair is healthy enough with this treatment to get compliments.
Everyone's hair is different, of course, but I think some of the women who are contemplating going the no 'poo route would be well-served if they just started using less shampoo less often and applying it only to the scalp, rather than to the whole length of the hair.