You will not find a single person in America who believes advertisements are a good neutral source of information, yet they still run them. They run them ever for products everyone has heard of and probably tried at some point. Why do you suppose that might be?
It's all about name recognition. Ads work because they stick the advertiser's brand in your brain, along with some warm and fuzzy feelings. The next time you're hungry on the road, and there's a McDonald's across the street from a Burger King, whoever has your warmer and fuzzier feelings will win.