Because the bank belonged to Mr. Qiao Bafu, an Imperial banker, no matter whether you had legal Federation status or not, as long as you were an Imperial person, you could open an anonymous account there and deposit money.
Of course, they also offered checking services, but more people preferred cash, so primarily the bank dealt with cash deposits, withdrawals, and loans.
Because Mr. Qiao Bafu had significant influence among the Imperial population in Golden Port City, many people trusted him very much and thought of him as the "Light of the Empire," so they deposited their money with him.
The large amount of funds gathered made it easy for him to make money from money, and some also said that he was secretly laundering money for some Imperial nobility, but nobody knew for sure.
Now, the usually not so busy entrance of the bank had started to see queues.