Being able to be part of Adsense and ranking for search terms are completely different things. And even if everything were integrated, the bar for kicking somebody out of Adsense would be much higher than demoting somebody in the rankings. Kicking people out of Adsense also is much more permanent, because Google has all of the person's information so they can easily block future attempts to signup if they kick you out.

The #1 thing Google is concerned about for search is webspam. The #1 thing they are concerned with for Adsense is click fraud. So in this situation, we probably have a) a site which gets little traffic because google search has detected it is webspam and b) a site which makes little money because it gets little traffic, and c) doesn't engage in click fraud. Therefore, it still is a member of Adsense, but gets no search traffic in google search.

Ads and Search are kept very far apart from each other organizationally, so things that search knows about a site may not always get over the firewall to Ads. This is an unfortunate consequence of the sort of Church/State separation we've set up that is in most ways very beneficial.

Not always - they let doddgy "helper" sites that charge a fee for things available for free from government sites e.g. passport applications back in after they added some minor tiny text to their site.

http://www.theguardian.com/money/2013/apr/15/passport-applic...