Those big companies can simply rely on the amount of informations they get from their own services.
Google has a service for almost everything, Amazon knows exactly what you want to buy and like google is extending to all the aspects of your life with digital services and Facebook as well has apps people spend enough time in to obtain informations about their interests. So their ad networks could work without cookies. But they also rely on fingerprinting that’s done through the ads themselves and the analytics tools almost every website has.
Google has a service for almost everything, Amazon knows exactly what you want to buy and like google is extending to all the aspects of your life with digital services and Facebook as well has apps people spend enough time in to obtain informations about their interests. So their ad networks could work without cookies. But they also rely on fingerprinting that’s done through the ads themselves and the analytics tools almost every website has.