everything naturally will gravitate toward people gaming the system. Its not just limited to shopping and reviews. Politics and social media behavior is not too different. If the option exist its going to be exploited, you either follow through or get left in the dust
Its sad that this is the way things are done but what can you do about it really? You can't fight every battle you need to pick what matters
Basically, once some start gaming the system - the others have to follow or they are dead.
It's similar to how irregular migration or general screwing over of workers works: if some farmers are paying 'under wages' or some factories are 'undercutting' ... then the others stand to lose business and are sucked into the same practices.
It's one thing when a massively successful entity like Amazon does shady stuff, but for most businesses ... it seems to often be kind of a quandary.