Galleries are often the place where new artistic talents are revealed. Owners of galleries check with local studios and art suppliers to find new artists in the area. Some galleries are large enough to have art buyers on staff. These people hunt through local shops as well to discover new artists. For any gallery, discovering new talent is a boon. If the artist has great promise, they will often remember the gallery that first displayed their works.
When a new talent is discovered in the art world, they generally have a gallery showing. Some artists go on to fame and fortune, or at least a steady level of work. They may move to a new city or country. In this case, the gallery that discovered them will still sometimes be sent works they create to sell. This is one of the reasons galleries work hard to find new artists.