They need to be honest because they are risking losing followers and about where they are going to get funds to maintain and make a profit from their reviews, there is such a thing as an affiliate, take the case of gambling reviews if the operators of these gambling review sites are honest, they are likely to get more active referrals from casinos, people first look on how honest the reviews are before joining,
Lol are you serious? If you think that they have to be honest, find me a ICO rating site that can be trusted.
Fyi, they don't really care about being honest simply because they make more money by selling fake ratings to scams than they would by adds or whatever else they are selling on these platforms. On top of that, their business model is completely different than gambling review sites.