You'd be amazed at how many do. For anything, from insurance to computers. The provider of one's car insurance is a regular discussion topic among those of my colleagues who have a driver's license, and I've seen at least two or three people lamenting about how bad the services they got were and switching to another insurance company on a whim, based on nothing other than the success stories of a handful of people.

Product comparison and review sites, or even Amazon, tend to be perceived as very broad and impersonal, while your bros know exactly what's best for you. I mean that's why they're yo' bros.

I have little doubt that this is economically, and to some extent socially self-destructive, but so is a lot of what we see today :-).