Marketing and brand recognition.
Most people don't really do their shopping based on quality or features, although that is changing somewhat with the internet revolution of the past years.
Names are drummed into you through advertising of all kinds, including sponsorships of your favorite photographers, or your knowledge of what equipment a photographer used.
People are always looking for an easy step up, and often that means they will emulate their idols, or at least fall prey to advertising. After all, how many repetitions equal one truth? According to Goebbels, it was 50, according to Huxley it was something like 40,000.
Why on earth would you buy a "Mercedes" bicycle, when you can get a better one from Haro for less money, and more features? The recognition of the brand, and of course the ubiquitous desire to have "status." Only a bike enthusiast, and even then a fairly knowledgeable one would know the name Haro.
We sometime-Luddites are a bit more immune to these things than many other people, but we fall prey as well. What if you heard a rumor that Xiktmol film, a brand new product, was so good it was silly, and had finer resolution and grain than Ilford Kodak or Fuji? You might go into the store, but chances are, you will reach your hand out for the name you know and trust, just like mother's milk.