In civilized nations the government is not allowed to enter your home unless either you have consented to it or a competent court has issued a search warrant. And in a descent society such a warrant is only issues if there is a good cause, i.e. a reasonable suspicion of criminal activity.
Privacy is an important good in a liberal society. Personal freedom can only exist if citizens have the certainty that they are not the subject of arbitrary interference of surveillance. Otherwise it would be too easy to intimidate citizens into submission to the whims of others.
Your bank records tell more about you than your DNA. Your ATM or credit card activity not only tells what you buys, but also where you have been at what time.
If we demand that the government cannot search your home or place a telephone tap without a court warrant, then why not apply those same rules to obtaining bank records? The underlining principle is that the government should only enter the private sphere if there is a good cause, i.e. when the public good is at stake.
Bank secrecy is simply a logical extension of the right to privacy. Your bank should not provide your bank records to third parties, just like third parties have no right to read your emails. If the authorities have a reason to check your bank records, then they should first obtain a court warrant. In this way citizens are protected against arbitrary infringement of their privacy.
Unfortunately bank secrecy has got a bad rap. And not without reason as “off shore” banks play a crucial role in international tax avoidance. In order to prevent that space settlements got black listed because of their commitment to bank secrecy, certain measures should be taken.
For instance space settlements could implement the rule that only residents could open a bank account in their jurisdictions, and non-resident foreigners could only open an account if they can demonstrate they are involved in legitimate business in space settlements. Another idea is to impose a deposit tax of, say, twenty-five percent on depositing money from abroad. Such measures will make it less attractive to hide money from tax avoidance or criminal activity in space settlements.