Getting your book reviewed is the best sort of advertisement. Even if the reviewer is not greatly enamoured by your work there is always the case of all publicity is good publicity.
Publishers are familiar with literary agents and with editors and reviewers of magazines and newspapers. They are well practised in getting their product in front of the people who matter and who could well affect the sales of the book.
The book I have just finished was reviewed extensively. My Sunday paper covered it as well as every journal and magazine I picked up for several weeks. Interestingly, there are though markets that are not covered by reviewers. Mills and Boon books sell in vast numbers but they are never reviewed!