It's useless to "serve ads that have something to do with the stuff I'm looking at". I read an article about smart thermostats the other day. I don't need a thermostat, I rent a shitty apartment! My HVAC is wrapped into my rent, I don't even care how much it costs. I saw an ad for bleach laundry detergent on YouTube, which I would never use because I listen to punk rock and don't own white anything. I've pretty much stopped watching TV because all they show are make-up and tampon commercials.

The advertisers need trackers, otherwise they're just yelling into the void. It never used to be like this because people were pretty homogeneous. A few decades of globalization and multiculturalism have made us much more diverse, and an impossible target for generalized advertising.

I'm not defending them, just pointing out the challenges product-makers and advertisers face.