Let's say I own a railroad and you own a soap company. For years to get your product to consumers you pay me money and I transport it to stores to be sold. Now, I see how lucrative your soap company is, so I decide to get into the soap making business. However, I raise prices on how much it costs to ship your soap while lowering my prices. I also ship all my soap first, cause delays in shipping your soap, etc. People can buy my lower quality soap cheaper and stores make bigger profits so I ship continually more soap than you. Keep in mind your soap is what consumers want but they can't access it anymore (since stores stock less / supply is always limited / etc) so they have to by my lower quality soap.

Now replace "railroad" with "search engine" and "soap company" with "reviews" and you have the same situation with Google vs. Yelp or Google Shopping or Google Maps.

Essentially you're just stifling competition at this point and preventing the market from choosing products.