Comment by TeMPOraL

Because SMS is not considered a secure 2FA mechanism anymore, and hasn't been for a while. If that's the default for that bank, and not GP going out of their way to pick a legacy access path, then they're about a decade behind what's considered industry standard -- which today is querying a second factor not just per login, but also per important operations (money transfers, dispositions, changes in settings), with the second factor being by default a smartphone with hardware and software integrity verified via remote attestation.