Ads are actually more likely to provide the answer to your question, or the solution to your task, when you're searching for something to buy. Which may weigh into why Google puts so many of them on the page.
It's one of the things that prevents me from ad-blocking sites like Google. Some of the time I will actively be searching for the ads, and avoid the natural results, because the natural results for some product searches can be extremely spammy with "review" sites and comparison shopping sites with horrible user experiences dominating the results, while the paid results are usually decent retailers or distributors.
