The answer lies in chemistry.

There are many ingredient incompatibilities, especially related to pH and to electrical charge (cationic/positive charge; anionic/negative charge).

Many ingredients like delicate proteins (growth factors, etc.) cannot stand a low pH, nor can many preservatives. Niacinamide can turn into nicotinic acid if the pH isn't in the right range. Copper and Vitamin C can theoretically cancel each other out. Certain ingredients need a lower pH to be effective.

Then there is the issue of volume and potency. Most ingredients require a certain volume to be considered "active." You can only add so many of these active ingredients before everything starts to get diluted, and thus ineffective.

 

The exceptions? Certain actives like peptides, growth factors and stem cells. Such ingredients are measured in micrograms -- a unit of mass equal to one millionth of a gram -- and little volume is required for such ingredients to be very effective. That's why, for example, we're able to "shove" the top 40+ primary ingredients of TNS Essential Serum® into Reviv's Ultimate Serum AND leapfrog that formula by also including hexapeptides and stem cells.

 

While we wish we could provide a product that contained a sunscreen, antioxidants, stem cells, hydrators, brighteners, tighteners, telomere-targeters, glycolic acid, retinoid, emollients, redness reducer, wrinkle filler, anti-inflammatory, copper, vitamin C, etc. -- all in one bottle. It's not practical or possible. Be skeptical of the efficacy of any product that portrays itself to do it all. There is really no such thing as an "all-in-one" skincare product.