I'm guessing that the page gets skipped when you're on a familiar IP address with a familiar cookie, or there are other factors where the bank decides more authentication is unnecessary.
10 years ago I got a Mastercard that for the first time required me to answer a 3D Secure questing each time I did an online purchase. It's been at least seven years since I had to answer that question though. How 3DS figures my card carries no fraud risk I have no idea. Is my card less likely to get stolen? Perhaps they have geography as a metric?
