Where are you getting this "you claim to offer your content for free" from? Most sites don't make a claim the content is free, but people like to assume it is and take it. It doesn't put the providers in a good light that it's become the norm that there's an unspoken agreement going on that they are benefiting from, but it's not any better on the consumer side, as taking something without confirming it's actually free isn't appropriate either.
What we have here is an unspoken agreement about a transaction taking place, and both sides are interpreting it in their best interests without confirming that's okay for the other side. Everyone's an asshole in this scenario, which I think fairly accurately describes reality.
To put this in relatable terms, it's like walking down a country road and coming upon a crate of apples. While they don't say they are free, they look kind of free, and you're hungry. You take one, and all of a sudden a guy jumps out from behind a tree and demands that you owe him a favor and some info about yourself for eating his apples. He's a scumbag, it's obvious, for trying to engineer a scenario where he can solicit business from people that might otherwise pass him by, but the passerby that partakes without confirming that it's actually free isn't without fault either.
Now, we see that some people are pretty good at just ignoring the shop keeper, and they keep reaping the benefits of free apples. Sure, the owner of the apples is an asshole, but the other people are still stealing his apples, and regardless of how much an asshole he is, that's not okay. At this point, both parties are acting in bad faith. Unfortunately, the problem is muddied by the facts that people decided long ago, primarily due to these shady guys and small favors, that apples just aren't worth paying money for anymore, and rarely the guys that own the apples even sell your info and/or favors to really shady people, so it's often safer to ignore them and give them nothing.
P.S. Yes, this conflates the content creator and the ad network, but that's not really the point of this.