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As an AdSense publisher, I would like to know the same thing. There are tons of AdWords ads that appear on Google SERPs that would be appropriate for certain pages on my site, yet I'm getting ads that are targeted to the overall theme of my site rather than to the content of the page in many cases. It's not a situation of the advertiser opting out of content sites, because that same advertiser is appearing on other pages of my site.
Google has a lot of tweaking to do with ad relevancy. It took a serious turn south at the time broad matching was implemented in mid-October.