When a man wears his hair very short, he doesn't need shampoo.

I shave to the bare scalp and just use plain old soap.  I haven't bought a bottle of shampoo in years.

I use a single liquid "body shampoo" product for hair, body, and to wash my hands in-between showers.  I find the liquid form much more convenient that a bar soap product, especially when traveling, and also only having to pack one product.  When my hair was much fuller I did find a conditioner useful (no tangled ends when I wore it longer) but not that necessary.

This thread reminded me of a Consumer Reports article on shampoos many years ago, and the dizzying array of products.  The subtitle was "The soap in the shampoo is to clean the hair, but what's the 'fruit salad' for"?, referring to all the exotic ingredients some products contain.

When a man wears his hair very short, he doesn't need shampoo.

I shave to the bare scalp and just use plain old soap.  I haven't bought a bottle of shampoo in years.

Sometimes I prefer plain old soap on my normal length hair to cut the oil better than shampoo.