If you are a smaller publisher, unless you get particularly active in courting advertisers (i.e. spend time going into sales), the niche advertisers will never even look at your content. The 20-something digital ad manager has no motivation to risk his job doing speculative ad spend. As a result your ads are less relevant and your inventory’s CPM drops as a result.
If you are a large property, then tracking affects you less (in fact tracking might be worse for you). Large publishers already have sales and marketing teams and ad managers will just choose you because you are “safe”. If brands are moving to a world where tracking data is less and less reliable, then by default they will move to spending more money on a smaller amount of “safe” inventory