"customer onboarding journey" sounds altogether twee for a major international bank. Banks are mattresses with insurance policies. Why is there even a journey to be broken?
Because they have to know who you are in a fair bit of detail both to comply with the law and to know who they should let take money out of the account. Because they need you to agree to a bunch of contacts. Because they need to get you things like a bank card. Because they need to decide if they want to lend you money (most often in the form of a credit card). And so on and so forth.