[oblio]

True, but as you admitted, everything is "a known quantity", i.e. more or less frozen.

Which is cool when everything works and nothing has to change. When something breaks or you need to change something... you wish you had things such as clean code, unit tests or even TDD/BDD, code coverage, continuous integration.

Banks are basically sitting on systems they don't fully control. They're kind of an interesting experiment: how long can you control the dragon, i.e. continue operating via patchwork and outside contractors which are in their 60s? :)