Mainly due to proprietary hardware+software solutions which cannot be ported now and remaking them with new hardware will require redoing the same processes as before (probably with additional stuff added by later laws) all over again.
If you try to replace just the hardware, you get fun solutions like a modern computer with a VM running Dosbox on critical infrastructure. Hey, if it works and your boss is willing to sign off on it…
One thing came to mind, Irreplaceable infrastructure computer systems from decades ago.
There are powerplants and oil rigs that use computer from decades ago which is irreplaceable (either due to technical or cost effective).
Mainly due to proprietary hardware+software solutions which cannot be ported now and remaking them with new hardware will require redoing the same processes as before (probably with additional stuff added by later laws) all over again.
If you try to replace just the hardware, you get fun solutions like a modern computer with a VM running Dosbox on critical infrastructure. Hey, if it works and your boss is willing to sign off on it…