Their product is their reputation for good reviews. Destroying that is clearly against their interests.
For example, if vendors know that the site is reviewing their products, they can provide support or a higher level of service to the review and influence the rating.
Magazines like Consumer Reports go to great lengths to bake bias out of reviews, and avoid this sort of risk. But their process has its own problems, as it requires that the reviewers really deeply understand the product, or biases ratings towards customer satisfaction.
My own car (my trusty Honda Pilot with 300k miles) is an example. It featured a poorly handled transmission defect and recall, yet CR scored a very high expected reliability rating, due to historical owner satisfaction.
Caveat emptor applies as always but I agree with you the Wirecutter is a generally good review site.
I mean, that's exactly how bias works. In fact, this is exactly what amazon is cracking down on right now, incentivized reviews.
If your revenue model is based on ads, you grow revenue by growing readership which is grown by writing quality content. However if you're revenue model is based on affiliate income, you increase revenue by selling more stuff.
Well... not exactly...
They're cracking down on incentivized reviews on amazon.com product pages. Those onsite reviews being a far stretch away from offsite recommendation blog posts that feature affiliate links, which aren't included in any of their product rating/review metrics.
The review for a particular product isn't an example of pay for play because the Wirecutter gets paid for anything they review that is sold on Amazon. The bias is the push towards Amazon vs Newegg or Walmart and assessments if price based on ephemeral Amazon pricing vs MSRP.
The Amazon crackdown as I understand is about corrupt vendors incentivizing good reviews for shit product.