That's the whole point: you don't have to research the coffee because you already know what it's like. People don't like to pay for stuff they don't like, and they don't like doing research. So if you can somehow assure them that they are going to like what you're selling, that's worth a lot. I'd rather spend $5 on a cup of coffee that I know I will like than $.05 on an app that I don't know I will like. I don't trust the opinions of people on the internet, or even most of my friends in real life, so reviews are not that useful to me.