There is no implicit link between "stuff on the internet" and advertising, this "free service" isn't free, we're all paying a gateway fee to get into the internet to begin with, then many content providers have judged their content valuable enough to justify asking for payment, with others relying on soft/burst funding sources like crowdsourcing. The internet and most people's sites really aren't so expensive to maintain that we need this level of crazy marketing.
Why are they falsely entitled? You're choosing to give your attention to a site in exchange for its content. That was your choice. The site turns around and sells a tiny slice of your attention to an ad provider in order to actually make money. But make no mistake, this was the attention that you chose to give to the site in exchange for its content, and that site can spend your attention how it wishes. If you don't like how it spends your attention, don't patronize that site anymore.
Advertising isn't voluntarily entered into by us, it's forced on the consumer. Personally I try to avoid patronizing sites that use heavy advertising (except interesting articles forwarded to me) but I am more speaking on the harm to us all. I suppose I could reword my comment above a bit more accurately to "I reject the normalization of advertising in society."
But the simple act of "I placed an ad on this site, is that ad driving sales?" is perfectly benign, and if we can enable that use-case without enabling any privacy leakage, that's unambiguously a good thing because making the privacy-conscious approach easy and reliable means people will use it and won't resort to the more privacy-invasive techniques.
This is the same underlying justification as the "ping" attribute, which is basically, it enables in a privacy-conscious manner the basic functionality people want, and which they already have other less-privacy-conscious means to get, so let's make the most user-positive option the simplest and most reliable.
Also by standardizing how this works it enables content blockers to block these requests. This ad click attribute proposal even explicitly listed this as a feature. If you don't want ad click attribution, use a content blocker that blocks /.well-known/ad-click-attribution/ and you're done.