Until Uncle Sam comes up with some solid regulations to whittle the stream down at the bank end, if it's easiest and least risky financially for a bank to file, a bank WILL file. If I owned a bank I would do that too, after the whopping fines that the heavyhanded Fed.Guv has levied.
Obvious why more and more people are dumping US banks in favor of offshore banks.
There are regs with mandatory filing, but the government also leaves it up to the bank's discretion to file for any transaction that doesn't meet the mandatory filing requirements, but is still suspicious given the unique circumstances. Thus, the banks are probably playing CYA by reporting almost everything.