Those systems are usually boring things that never get modified. Ledgers, etc. The tasks required to process checks are the same as they were in 1975. The input

Those systems are usually boring things that never get modified. Ledgers, etc. The tasks required to process checks are the same as they were in 1975. The inputs and outputs just changed. Sometimes the COBOL isn’t the problem, it’s the scaffolding built around it. As an example, I worked in a consulting role on stabilizing systems during COVID that were getting crushed. The COBOL stuff on the mainframe wasn’t a problem - tweak the job control stuff, give IBM more money to lease more cpu time, and you’re good to go. The problem is the 1995-2005 legacy middleware dreck that isn’t engineered well like a mainframe app and doesn’t scale. That stuff is always hot garbage and makes it difficult to replace the backend mainframe. The middleware expects whatever comes out of the mainframe, you end him with a chicken and egg scenario. Financial services tend to have good data management practices and regulators who know how to audit for them. As a result are successful in getting off mainframes. Governments, manufacturers, etc, often struggle with that.