I think the reason for this is so people don't pass the keyword "mesothelioma" with every page, so the clicks are most valuable... from Google's perspective, it

I think the reason for this is so people don't pass the keyword "mesothelioma" with every page, so the clicks are most valuable... from Google's perspective, it's to keep people from "cheating" and serving non-relevant (but more profitable) ads to their visitors.