Sometimes I host people who have 5-6 nice reviews by hosts and who never (NEVER) bothered to write a review for any of them. I find that to be a rather shitty behaviour, and I do not review these people unless I have something to warn my fellow hosts about.
I also think that guests with no reviews should care enough to put in a small effort and write a review if they want a review in return, as they need this review more than I need theirs. I usually write them a review anyways. But I first and foremost see reviews as “messages” to potential and future hosts and this is my main motivation to write them. I mostly do not write them for the sake of my guests, unless they were exceptional.
I’m aware that this might be an unpopular opinion.