Google, Facebook, and The Creepy Line

Google also makes most of their money via this same type of keyword-based advertising that doesn’t require any search-history tracking.
So why do they track it all then? Because Google is not really a search company; they are an advertising company. On Google, your searches are tracked, mined, and packaged up into a data profile for advertisers to follow you around the Internet through intrusive and annoying ever-present banner ads, using Google’s massive ad networks, embedded across millions of sites and apps.
This is why if you search for something on Google, you may start seeing ads for it everywhere. Using the Internet doesn’t have to feel like you’re being watched, listened to, and monitored.
Google, Facebook, and The Creepy Line
Eric Schmidt, former Google CEO and Chairman, famously said “Google’s policy on a lot of these things is to get right up to the creepy line, but not cross it.” But for most people, that line was crossed by Google, Facebook, and others long ago.
Alarmingly, Google now deploys hidden trackers on 76% of websites across the web to monitor your behavior and Facebook has hidden trackers on about 25% of websites
Chart showing the percentage of trackers on major websites.

Source: What Is the Business Model for DuckDuckGo?