Because of how they are made, natural soap bars are alkaline. Hair is acid, so you need the acid rinse to restore the pH of your hair. A pH balanced bar wouldn't be acidic, either. pH might be lower, but not the same as hair.
3a (Corkicelli), highlighted, fine, low porosity
modified CG, since April '07
CG since 3/11/08
HGs: Anything Sevi; Curly Kinks Satin Roots, Curlycue ReNew and Coil Jam; homemade FSG and okra gel; soap bars; UFD Curly Magic; Botanical Spirits Jellies, CJ Repair Me