I have dry skin and eczema. Using bar soap on just my hands equals cracking and bleeding. Let alone attempting it on my body or scalp.

Also I have fine, coloured treated hair.

I use pretty standard supermarket brand body wash on my skin and somewhat expensive shampoos on my hair. I use mid range moisturisers. They're all enough to keep my skin in good condition. I'm not prone to breakout though, so my body doesn't need too much intervention.

My point is to say that I need that level of care in my products. Not at huge expense, but some. Your suggestion would have me literally itching and bleeding all over.

Everyone is different but there is a market for a spectrum of products. Bar soap is very unlikely to be the answer for most people.