Mattresses are a huge racket in general. Think about how often you need to buy a mattress and then consider how many stores in you area sell only mattresses out of expensive storefronts full of salesmen. The margins per mattress have to be astronomical to support a business model like that. But on the other hand they are very heavy and bulky which makes them expensive to ship and since people generally need to try several out before finding one that is comfortable they aren't great for an online business model.