I still have to support NT4, XP, VxWorks, Win98 and even some networked DOS machines in our factory.
You don't go changing the OS on a piece of equipment that costs over a million bucks to replace and all the software for the equipment is written for that OS. You just keep supporting it. And when you have hundreds of machines that cost a shit-ton of money to replace but work fine with the old OS, you keep supporting it.
And you call the new employees a buncha goddamn whiners because they don't want to learn "old stuff."
Knowing old stuff makes you valuable.