That is a great example. By not taking account of risk on the front end by embracing change, the system gets progressively more expensive to maintain (extended support contracts) and the risk of eventual inevitable change grows higher. Further, the system becomes progressively less valuable compared with newer systems.
> becomes progressively less valuable compared with newer systems.
Indeed, business people do not typically model depreciation curves for software as they should. That doesn't mean that the plant control system becomes less valuable (the value is tied to the operation of the plant, probably for the lifetime of the plant), but in many other situations it does mean that.
There are PDP-11s running nuclear plants today with support contracts to keep them running until 2050.
PDP-11s.