I've been in the soap making business since 2009. We make an all-natural powerful blend designed for men working in factories. Turns out women love it. But this is beside my point.
The real point is that I designed this stuff using as much science / true research that I could find. And there's almost nothing out there. In fact, I still haven't found a shred of research that proves why soap works. Does it dissolve cellular membranes (as I was taught in school long ago?) or does it increase the tiny forces acting against their anchoring ability so that they wash away in the great flood? We really don't know.
And my guess as to why we don't know is this: We have 'known' it works for several thousand years. Therefore, if I'm applying for grant money to 'prove' this, I'm going to be laughed at. There's no money, no potential money, not even any potential bragging rights for being the guy that proves soap works.
It may be that our recent discovery of the microbiome will change all this. I hope it does. I can tell you from personal soap-selling experience now, and interviews with hundreds of women, that it really is far more complicated that it first appears. I used to think I knew the answers. Now I just have lots of questions. And my personal advice as for the majority of washing that we do? Water. That's it. Just rinse and you're done.