COBOL and many legacy systems have the nasty problem of everything being inter-connected: a textbook example of spaghetti code. So in such systems, in order to

COBOL and many legacy systems have the nasty problem of everything being inter-connected: a textbook example of spaghetti code. So in such systems, in order to even begin properly, you have to rewrite a sizeable chunk of the legacy code before you could even showcase a first demo / MVP. Needless to say, the relentless culture of our modern times makes the businessmen never approve such projects.