And it's not about ego. Authors don't chase down reviews to feel good about themselves but because it gives new and potential readers some insight into what kind of books they write. I can say whatever I wish in my YouTube videos but sometimes what people want is an outside party's point of view. What kind of book is it? Was it a fast read? Did it keep you hanging on? Was it exciting? Did it leave you wanting more?
Not that authors don't appreciate positive comments outside of reviews. We love them!! Unfortunately, people who aren't familiar with us or our work might be skeptical. Many readers stick with the tried and true authors, the ones everyone is raving about online and whoever is on Oprah's reading list, and that's understandable, but it makes our job finding readers challenging.
A review can make a difference. I know I've certainly hesitated to purchase a product (especially online) unless I could compare reviews to see what other people think. And if you're an indie author like me, it can help make you stand out from the crowd.