That's vastly more expensive, though. Now you have to run extra servers to make outbound connections to the ad tracker's API server instead of turfing off all the work to visitors. It would be enough to significantly affect the ad market.
I could even see a data broker centralizing this and distributing tracking to all of their clients. The client would just need to communicate with the central broker, which is not hard at all.
BTW, I see this as a feature, not a bug. I'm glad it would be harder and more expensive to violate my privacy.