Tell that to the guys who invested in Coca Cola when it was first launched ;-)
There is some truth in your statement but also a disclosed formula does not, per se, ensures any higher revenues so you can not simply confirm that a proprietary blend would diminish top line and even less quantify by how much with a high degree of certainty.
As everything in life, there are pros and cons and business is about making decisions. Most of these companies are of private capitals and as such the need to protect/increase the value for the share holder is not part of their objectives so it all becomes a subjective decision based on the beliefs of the owner/management. We could discuss for hours, but the only truth is the reality and as such we can see companies taking both paths and in both paths we have very successful companies so it is hard to say which path is best.
In my case por example I don't run away from a proprietary blend product if the reviews and results are positives.
Coca-Cola is a completely different beast because they were original. Also, comparing food and beverage to supplements doesn't really apply unless you specifically overlap them. For example, if you create a protein water with 50 grams of protein, 50 calories, 0 sugar, and it tastes just like orange juice then the prop blend for that flavoring would be valuable because it would give you a competitive advantage over the competition. However, if you decide to also throw in a prop blend of branched chain amino acids into the drink, then where is that value in that prop blend? Why is that prop blend of BCAAs worth more than any other BCAA blend or profile? The short answer - it's not.
Now, I didn't say that less people would buy supplement products if they had a prop blend, however I questioned whether or not they would. Perhaps more people would buy a prop blend as opposed to a detailed profile.... My assumption is that less people would buy a prop blend, however do not take that as fact. I would assume supplement companies have researched this before and should have the answer to it. My true argument is that there really is no
value in a prop blend in the supplement industry. Patented ingredients? Well that can be valuable. But I can't think of a single prop blend out there in the supplement industry that is actually worth anything. The only value of these products I see is the cash flow they produce.