Where are you going to find a young engineer who wants to build a dead-end career? I'm sure that if you pay them enough, someone will show up, but most people would rather build skills that will continue to be useful rather than skills that will be useless once an inevitable, sorely needed refresh happens.
I think you overestimate how much working on obsolete tech is a dead end career. Skills are still transferable. Someone who can sling 8086 assembly can figure out your dumb web app.
The replacement will use modern parts and tools, administered by someone who knows modern systems.
There is no use in becoming an expert in an ancient system ridden with proprietary and obsolete parts, just so you can help one city maintain their ancient system. It's even worse than wanting to become a professional fax machine guru.
There is no use for so many things…
For example there is no use in assuming you know what other people want to do with their time, because you just don’t know.
Some people like knowing unique things, or just enjoy learning, or want to be a small hero for a small group of people, or are just curious.