Because, on the whole, banking is one of the industries with relatively high and stable income level in China. Although there is no such thing as an iron rice bowl now, it is no problem to live a well-off life as long as you don't make mistakes.
Planning this kind of work, there will always be opportunities, even if one day you are tired of working in a bank, you can find an advertising company when you come out. However, the door of the bank is not open every day!