The reason why there are so many employees in the sales industry is also because of its considerable salary and working conditions that will pay off as long as you work hard. Because the sales industry actually relies entirely on the usual performance besides the basic salary, you can get as much money as you are willing to work hard.
For this kind of job, many people with little income and no feelings are actually willing to take this job.
Moreover, there are many people in contact with the sales industry, and more people can improve their ability and attitude towards the world. There are thousands of people, everyone is different, there are good people and scum, and it is not necessarily a bad thing that the sales industry can face more people.