I know lots of advertisers think they can't live without it --- because promoters have told them so.
No, it's because they want to make as much money as possible.
If promoters told them to turn off all ads, they wouldn't. They don't care about promoters. They care about money.
The promoters of personalized advertising care about money too.
The auction systems they promote can be easily manipulated to maximize profits. And since these systems are "black boxes", advertisers themselves really have no way to know if they are being manipulated or not. The only insight they have is what the promoters tell them.