I'm a woman and I haven't shampooed my hair in forever. The last time was probably 8-10 years ago. My hair is clean. It's soft. It smells fine (my husband always tells me he loves the smell of my hair).
Shampoo is a recent development in human history. People survived for millennia without any commercial products for their hair. Stripping all the oil from your hair and scalp just sends signals to produce more, and quick! The companies that make these products have brainwashed us into thinking we're nasty if we don't buy what they're selling.
I do realize that people have different skin and hair types and just because it works for me to eliminate shampoo, it might not work for everyone. But not using a commercial shampoo has made my hair much healthier and more manageable than it ever was during the years I did use one.