You make a good point, but think of it this way. Someone Googles “tips on buying a new laptop”. Companies enrolled with the Google program bump up their prices for that user. But what about websites not enrolled in the program? Their prices stay lower, so if the person buying the laptop ships around even a little bit, they will likely buy from one of the non-affiliated sites.
It only works if the whole marketplace is under the system. Amazon is a shopping experience tailored to keep people inside their system, so it works with them. You aren’t going to take the time to price match across multiple websites for a pair of socks. I think it is a lot harder to manipulate prices with big-ticket items, where people will put in the effort to shop around.
Absolutely agree, but at some point there will still be someone reporting expenses to the government and that needs to be trustworthy info.