From The Electronic Freedom Foundation:
The behavioral advertising industry claims that it can deliver more value to everyone through this surveillance: advertisers get to target exactly who they want to reach; publishers get paid top dollar for setting up exactly the right user with exactly the right ad, and the user wins because they are only ever shown highly relevant ads that are tailored to their interests.
And as to the claim that users “like ads, so long as they are relevant,” the evidence is very strong that this isn’t true and never was. Ad-blocking is the most successful consumer boycott in human history. When Apple gave iPhone users a one-click opt-out to block all surveillance ads, 96 percent of users clicked the button (presumably, the other four percent were confused, or they work for ad-tech companies).