This question already has an answer here:
Why is there no SE site dedicated to questions about beauty, cosmetics, skin care and related questions and answers?
There’s millions of different beauty products, but almost all information you can find on the subjects are sales pitches from various companies. This seems like a perfect opportunity for SE to serve a massive market.
There is a related meta question discussing alternative SE sites, but it doesn’t explain why there is no dedicated beauty Q&A site.