Hong Kong/Hangzhou/Beijing —  When humanoid robots dominated the stage of last year’s Spring Festival Gala with sleek dance routines, Ai Lin saw more than a spectacle. He saw a business. Soon after, the e-commerce livestreamer in Hangzhou shelled out $30,000 for his first android and turned it into a rental venture. Business has been brisk. For 3,000 yuan ($443) a day, customers can hire an android to attract crowds at exhibitions, perform at events or even help stage a marriage proposal. But his venture has also revealed what viral videos of dancing, flipping Chinese robots have not: the heavily promoted technology...