I can understand why the big banks are reluctant to re-write the big systems now that they have painted themselves so far into the corner, but what I don't unde

I can understand why the big banks are reluctant to re-write the big systems now that they have painted themselves so far into the corner, but what I don't understand is why they seemed so disinterested in the massive advances that were made in the 1970s that would have made COBOL and IMS long obsolete already then.