This would be great obviously but the problem here is that information based results are not generally selling anything so they are no good to Google.
Studies have shown that consumers typically research purchases over a period of time (anywhere up to several months) before actually buying, so focusing exclusively on "transactional" SERP ads is leaving money on the table. (That's probably one of the reasons why Google introduced AdSense.)
If searchers were able to express their "informational" or "transactional" intent (as opposed to Google's trying to divine it), Google would be able to do an even better job of matching ad messages to its search results. The SERPs would be better, and the ads would be more effective. Searchers would benefit, and so would Google and its advertisers.