Well firstly, I'm not sure the site author knows the demographic. I'm pretty sure he doesn't ask that sort of thing before doing the calculation.
Secondly the way Google determines the demographic is via the site content.
Or to put it another way; site owners don't have a "right" to Adsense. Google is clearly allowed to choose those sites it considers "to be good advertising sites".
Therefore if you have a site that doesn't offer good advertising opportunities, then don't be surprised if people don't want to advertise on it.
To be clear, I'm not saying all sites should be ad friendly. I'm saying that advertising alone cannot prop up every site, useful or not.
Google has a monopoly though. Multiple monopolies even.
If Google had competition in the ads space, this would be less of an issue, as the author could pick an advertiser that works for their website, rather than contorting their website for google
Tell me more about the advertising potential an alternative advertiser would see in this site?
Or to put it another way, what product should this be advertising on this site? Because there are a lot of companies in the world, so of you can identify just one of them, they'll likely pay enough for exclusivity.
I would think this tool is useful for students or journalists. Grammarly and other writing tools would be relevant. Obviously, people who are interested in government or politics, so political ads are hugely relevant.
Secondly the way Google determines the demographic is via the site content.
Or to put it another way; site owners don't have a "right" to Adsense. Google is clearly allowed to choose those sites it considers "to be good advertising sites".
Therefore if you have a site that doesn't offer good advertising opportunities, then don't be surprised if people don't want to advertise on it.
To be clear, I'm not saying all sites should be ad friendly. I'm saying that advertising alone cannot prop up every site, useful or not.