I strongly disapprove of private trackers. I'm forced to take part in some only because the content isn't available anywhere else. And the private trackers generally forbid re-sharing their content on public trackers, which unnecessarily gatekeeps the content and perpetuates the problem.
If it doen't help to make everything accessible to everybody then it's not a valuable part of the sharing ecosystem.
Making their service more attractive to customers is precicesly what they're trying to do.
It's just that an advertising agency's customers are not the folk who watch, read or hear the ads, it's the folk who pay for the ads.