Why do accounting firms always hire audit assistants? Is it because cheap labor runs out and they kick it away?

I don't know where you are, but 50 a day is really cheap. As for retaining people, unless you are particularly excellent, especially some small clerks are really unscrupulous, just to recruit a group of labor during the peak period of business, and you will hardly leave a few after the peak period.

For fresh graduates, it is good to exercise if they are in a big university. Audit practice is of great help to accounting business. But don't expect someone to teach you. The company will basically treat you as a member of the assembly line, and all the programs and formats are designed. You are just a digital porter, so if you want to gain something in your internship, you have to read more, ask more questions and think more yourself!