They need that list for max profit. Just serving ads without an intelligent platform behind it to know where and when to serve them, will hurt the CTR (which hurts both the ad tech platform and the advertiser).
Why would ad tech companies gather data and invade your privacy, and then not use it to sell more profitable ads? That makes no economic sense, but is a costly form of voyeurism. The "myth" you refer to sounds like a poorly thought out conspiracy theory.
Why would ad tech companies gather data and invade your privacy, and then not use it to sell more profitable ads? That makes no economic sense, but is a costly form of voyeurism. The "myth" you refer to sounds like a poorly thought out conspiracy theory.