Think about it, Google Maps is (I think) the biggest collection of map data and information on locations everywhere around the world, yet I don’t want an advertising company knowing that I just went to a fast food place.
YouTube is an endless trove of video content that anyone can contribute to, yet I’d much rather not give an advertiser information on every little interest that I have in video.
It’s so bad for you, but it’s so good.
It just shows up because it’s popular and they don’t reasonably know what you like.