Trial and error takes time. Potentially a great deal of time. A motivated fraudster will likely get caught and stopped several times along the way if they're at

Trial and error takes time. Potentially a great deal of time. A motivated fraudster will likely get caught and stopped several times along the way if they're attacking a particular bank. It's worth bearing in mind that most financially motivated criminals are after easy marks. If you're too hard or expensive to hit, they'll find another target. If you're seeing like a bank, that's a victory and the protocols are doing their job by reducing fraud.