Such an efficient model would show me very few ads indeed, as there is very little I need that I don't already have, and I resent being encouraged to spend wastefully.
Advertisers don't want to spend wastefully either. So if they know you won't spend, then you shall get less ads.
Eventually all the ad dollars will be spent changing you into someone who does want to spend more money.
That's propaganda, brainwashing, whatever you want to call it. But by my definition (the one I'm talking about; I didn't create it) it's not advertising, and I think Google is working to achieve my definition of advertising.