Ha, the pessimist in me says companies are out to make money, so they tell consumers what they want to hear, and a surprising number of people are willing to leave it at that and buy the company line of BS.
I'll give you an example. I've been raising tortoises for years, and as part of that I run something of an advice line to help people out. There are a staggering number of products marketed for tortoises that are completely unsuitable for them, and many are actually potentially deadly. You would not believe how many questions I get from people keeping their tortoises improperly because they buy products based on marketing, even though information on risks of using such products are readily available online. They just believe what the companies tell them, I guess because they think that "someone" would stop the companies from selling the products if they were unsafe. I don't see that it's any different for hair products, or any number of other products. Not that there aren't good companies out there, but it pays to know what you're buying.
Former longhair, now CG, living in N. California where the fog meets the wind
3a/b, fine, normal porosity/elasticity, high density
Conditioner wash and style, sometimes with a dab of BRHG.