Why are many companies selling job fairs in Shanghai?

You mean, most of them are for sales positions.

In fact, it is not only in Shanghai, Beijing, but almost all over the country. It may be that business managers think that sales can test and train talents best. They believe that the most direct window to understand an enterprise is sales, and the most basic thing is sales. If the recruited talents can't even do sales well, they can't be competent for other positions. If they are qualified, then they have the opportunity to stay in the company and continue to develop. To put it another way, many enterprises now produce with sales belts, or simply sell them. Sales is the first department and the center of an enterprise. Although I don't entirely agree with you.