Ad networks can offer to optimize the impressions, help to with targeting.
After all the current implicit user profiling and targeting is already not a 100%. Many people use adblockers, many devices are used by more than one user, etc. (In this day and age we are still baffled how Amazon/Google/whatever advertises us - for days - the same fucking thing we just purchased yesterday. Of course, because based on their model it's still the most likely thing the user might buy or click on, etc.)
Google seems to be already moving away from individual profiles with FLoC - of course they still want all of the data to be able do dynamically allocate users to cohorts (to maximize their profits).
And this is why Tiktok and Instagram just went ahead and are now doing direct sales. (They put a link on the video overlay where the user can go and buy whatever shit the video talks about.)
> isn’t a win for [...] sites
this is something that a lot of people are pushing back on, because their claim is that we need some slack in the system for sites to be able to pursue their own creative vision (however lame, banal, mundane, or seemingly useless it is). before every click was tracked it was okay if some article (or video) underperformed, because in general the advertiser got the increased sales (or brand awareness or whatever they measured)