That is a problem, because what I tell people all the time is that your data is money. Ad services also serves as a tracking service, and as such gets paid from two directions: from advertisers and mass collection of data.
The problem with both is that they have been devalued in a race to the bottom, mostly thanks to ads swarming the web in the early 2000s.
This also solidifies Google’s monopoly, because now all advertiser’s have to go through them, as well as Meta or other social networking platforms - which all have their own tracking and ad services.