Just to clarify. While it's true that neither guest nor host can see (for up to 14 days) the other's review until they've each submitted a review, that limit ends after 14 days. At that time, any review left by either party becomes public, whether the other person left a review or not.
That said, I don't believe that the reviews that I submit as a host should be influenced by whether or not I think the guest will leave a review (or, for that matter, a positive or negative review). I leave MY reviews for the benefit of other hosts, who can use them to decide whether or not to accept a particular guest.