Why do Dafeng (Shanghai) Computer Co., Ltd. not want Shanghainese for summer jobs and winter jobs?

Factories in economically developed areas generally don't want local employees, and they will think that they can't bear hardships and stand hard work (of course this is prejudice);

A few years ago, the demand for summer jobs in Dafeng was still very large. I don't know how many summer jobs have been used this year, but the factory will not default on employees' wages. There is no doubt that work is usually done in two shifts, that is, from 8 am to 8 pm.