Often, you don't, because the same developers of the bank app decided it's an unnecessary power user feature that doesn't fit in the MVP or something.

Or, even if they add it, there's no way to save the file, only to "share" it, which 99% of the times isn't what I want, and I'm frankly tired of routing through the mail app as a workaround. At this point, at least on Android side, there exist apps whose sole purpose is to be a share target and dump the information to file (and being apps on an app store, chances are top 10 are just thinly veiled malware).