For most early stage startups, user experience, like marketing and human resources, is a luxury. A bright idea is born, and few people hurriedly work towards developing a building a tool or a service that meets a need.
In many cases, however, this need is assumed. And, in those same cases, this assumed need is wrong, or at least not close enough to be make the purchasing decision easy for your customers. At the end of the day, this is really the only thing that matters: making sure that someone will use/buy what you have to offer.