It's been a while since I worked at a bank, but most there core stuff was running in a mainframe and while "modern" front ends exist, the core work uses terminal access.

A key thing modern replacements lose is the input buffer: One can type multiple screens ahead. In a modern GUI application I can enter a shortcut, but then have to wait till the corresponding view/popup/window appears and registered it's event handlers till I can put in the next command. In a mainframe-style TUI, if I remember the sequence, I can type ahead the shortcuts and input for next screen(s) before it's ready. For the experienced user, who runs the same sequence often this is really efficient.