You are forgetting that Google effectively has two groups of "consumers". Ordinary users who use their products, and companies that advertise using Google's products.
Even if ordinary users can switch to Bing the advertisers can't shift so easily as they aren't concerned about accuracy of search results but about the potential market size.
Even if ordinary users can switch to Bing the advertisers can't shift so easily as they aren't concerned about accuracy of search results but about the potential market size.