Marketers want to promote their products and increase sales. Consumers want to buy products which are good for them: they may want cheaper products, more high-quality products or products with special features. Although it may be hard to choose something because there are too many kinds of products.
Many people tend to reduce the amount of thinking if they can, it was probably a useful trait for our ancestors. Human brain uses a lot of energy for such a small organ, but contemporary people starve less often than our ancestors, so we don’t have to constantly reduce brain activity. Still it is an easy thing to do.
Marketers have to work better than marketers from other companies, so buyers would prefer their product. Marketers can use cognitive biases because they are useful to help sales of a product which doesn’t have real advantages. For example, the halo effect can be used to attract attention to a regular product. Marketers can also use logical fallacies to persuade to choose their product. For example, an appeal to authority often used, when a celebrity used to recommend a product.
But all these devices would work only if people prefer to think less, to use mental shortcuts. I can say that in this case marketers think for consumers. What consumers can do? Basically they can start thinking for themselves. Many things from advertisement texts to arrangement of products in shops can be analysed and considered before making a decision. Cognitive biases and logical fallacies can be found with careful examination. People can even train habits to detect sudden emotional changes and suspicious impulses to do something, then track these events to their causes.
All of these may sound complicated, but even complex thinking becomes easier after time because the human brain adapts to frequent mental activities. So after practice analysis like this would be done with less effort.