Kill Ads That Follow You
You know the problem. You shop for some item, maybe on Amazon. The next time you go to Drudge Report or some other site, there a photo of the product you looked at. It's annoying.
Google knows it's annoying. That's why it has adopted a new service: stalker ad blocking. Read about this here:
Google's marketers are clever fellows. They know that if you can avoid the stalking ads by using Google, you will be more likely to Google as your default search engine.
Every time you use Bing or some other search engine, you will see stalker ads on the pages you land on. You will be reminded of just how much you hate them, and just how nice it would be to avoid them.
Marketing. It's all about marketing: Amazon vs. Google. Take your pick.