This kind of thing is also used to ask questions. You think this is your home, and you want to be a massage technician yourself? Just go to a shop on the street and ask. Besides, who doesn't have an ID card in China now? You want to hide your identity, run away if something happens in the future, or do something bad to prevent the public security bureau from finding you so quickly. Anyone who doesn't want to reveal his true identity outside wants to leave himself a way out.