So to answer some of the questions. They are expensive right now but prices are coming down. If they become affordable (say $500-600) and you can buy designs like how you would with apps for your smart phone, would you? Some printers are now able to print with other materials like metal and ceramic. So you could actually create useful parts.
Companies, artists, designers use these to create 3D models before they go full scale. But on a more simple level, consumers can use these for a hobby or create parts that can be used. We want/hope for them to be almost as common as ink jet printers.