There are still lots of systems from the 70's and 80's running today. There are many PDP and VAX systems that run parts of the US military, such as missile defe

There are still lots of systems from the 70's and 80's running today. There are many PDP and VAX systems that run parts of the US military, such as missile defense and nuclear ICBM systems. Many airlines and insurance agencies also run on mainframes from that era. Even if they don't run the actual hardware, they're likely to be running the same software and OS on an emulator running inside modern hardware. It's simply too expensive and risky to rewrite all the software on a new platform.