Reviews also need to be monetised and the best wy is to make sure you are doing them with some profit, like getting paid tips by people. If you monetise by the casinos that are reviewed you would not be able to be independent and the public would loose confidence in them. To get tips and audience you will need to often update the reviews to get good rankings in searches.
I do not think anyone or any gambling site may give tips for monetise reviews but they may get some tips only from new gambling sites. And only new gambling sites may pay for reviews. I do not think any reputed sites may give any tips or may inspire any review sites. They may for only for those review sites which are too much reputed and which may affect their business, nothing else.