What a review does for a wavering visitor
At the moment a visitor is considering a booking, a review does two things at once. First, it works as social proof: someone with a comparable trip has already made the same choice, and it turned out well for them. A long text from a rental operator about quality weighs less than a short sentence from a guest who spent a week there.
Second, a review carries concrete information that the official description of the accommodation does not. How quiet it really is at night, how clean it is on arrival, how the operator responds to a question during the stay. Doubts a visitor does not voice while reading the page often find their answer through a review.