There’s nothing very sinister in this as it relates to mainstream travel writers: they are obliged to acknowledge the source of the funding ( and reviews can be read through that prism). It gets murkier with travel bloggers, as they rarely acknowledge if they are the beneficiaries of free goods/services, including preferential treatment ( some do acknowledge, or decline to participate, and they deserve credit for it and to be taken more seriously). At the really murky/sleazy/corrupt end of the scale are the “social media influencers”, ie paid shills/agents of corporations,. And there’s all sorts of jiggery pokery going on in that space.