Earlier quoted context omitted.
If that were truly their goal, their ads would never be the useful, because if they were the best results, they would be duplicates of the organic search results (hence useless). Or, if they weren't the best results, then the best results are in the organic search. Clearly that's not the case, as advertising makes 99% of their revenues.
the point of ads is not to be maximally useful, it's to maximise some function of (usefulness to you, profitability to the advertiser).
I'm not disagreeing with the fact that ads are subject to a whole different objective function. I'm saying that if the best results were already in the organic, then the ads would either be redundant (for the user) or otherwise less useful than the organic (by definition, really).