Don't sweat about the occasional guest who does not leave a review. Some are on a long trip and miss the 14 day cut-off. Some people just don't like to do it. If they were a good guest, you can gently prod them to leave a review when you have your check out conversation, I say something like:
"thanks so much for staying with us, I'm going to leave you a great review, tell your friends about us and please come back"
For the rare bad guest it is vital that our (the hosts) review appears whether the guest writes one or not. So don't get all worked up if a really nice guest has not left a review, even if you left one for them. They were nice and you got their money.