Currently: Advertisers can track you and estimate whether you are likely to buy the product. This is good for advertisers. If a user-controlled resettable ID

Currently: Advertisers can track you and estimate whether you are likely to buy the product. This is good for advertisers. If a user-controlled resettable ID prevents advertisers from doing this, what incentive do they have to not use their existing methods (in addition to the advertiser-ID)? Further, why would they not use tracking to say "Well, they reset their ID, but I know they're the same because of this other data, so I'm gonna link it back up behind the scenes."