For a variety of reasons - Old on-prem mainframes - Old mainframes hosted by vendors - Network latency (cloud <--> on-prem, cloud <--> vendor) - Requir

For a variety of reasons - Old on-prem mainframes - Old mainframes hosted by vendors - Network latency (cloud <--> on-prem, cloud <--> vendor) - Required sequence of calls (auth -> account list -> account balances) I'm not defending it. Many of these systems should be updated but the banks are notoriously slow to act and risk-averse.