Because they didn’t upgrade their systems in time while deep knowledge of these systems were intact and would have made upgrading seamlessly much easier. Now they have black boxes that no one truly understands anymore, so they’re paralyzed by fear and that’s what’s keeping them trapped in these old systems.
Why do the banks use COBOL? Why does NASA use FORTRAN?
Aviation use X400 and X500 which is bank SMTP.
Because they didn’t upgrade their systems in time while deep knowledge of these systems were intact and would have made upgrading seamlessly much easier. Now they have black boxes that no one truly understands anymore, so they’re paralyzed by fear and that’s what’s keeping them trapped in these old systems.