For one, Google could identify you since on Chrome you might have your name, address, and phone number saved for auto-fill, and sell your information to companies. They could sell your information to a certain company if their AI identifies you, for example, as a left-wing elderly male. I think the recent documentary that got deleted off Youtube explains it.

Google also censors results a lot compared to Yahoo and DuckDuckGo so you'll mostly get popular sites. An example is how when I searched "youtube deleted documentary" Yahoo and DuckDuckGo got the right results but Google didn't.

For Youtube, it dominates video uploading so it can delete and censoring things easily and all you can do is complain.