Are you purposely posting in the CP section?
People who make soap from scratch do this to have control over their ingredients and to come up with their own recipes.
"Real" milk can be used frozen (to slush) to make the lye solution, added to the oils in a certain percentage while the lye solution is made with the remaining % of water or in powdered form.
Melt & Pour bases are sometimes added to allow for more creativity/transparent inserts or swirls, not to add any benefits.