Most dealer carry brands that they think their customers will like, subject to availability if the brand in the area. So a dealer will carry a portfolio of brands to please as many of his target clientele. His job, and to be successful, is to sell equipment that fits the needs and desires of his customers, to make them really happy and come back. I know a few of these. They will go so far as to recommend something to a client that they don’t sell.
Now what happens at Best Buy and poorly run low end audio stores, that’s a different story.