Systems reaching the end of their usefulness may be scrapped, but there are other options.

Systems can be upgraded so they will last longer or perform better.

Systems can be replaced with newer versions with higher capacity and better quality.

Systems can be repurposed to make other products.

Systems can be sold cheaply and transported to developing countries.

Parts of decommissioned systems can be saved and used to support other systems still using them.

Systems can be abandoned in place, perhaps to be run when their newer replacements are down.

I created and installed modern, Level 2 supervisory control systems for old and new furnaces, sometimes replacing older Level 2 controls.

I've seen old newsprint lines be converted to produce specialty tissue grades.

I've heard of old production lines being disassembled and transported to Africa.

We used to take computer boards from old VAX systems, hand them to a flight attendant on a plane at the airport, and have someone from the destination airport receive the board and use it in their plant to keep an older system running. (This obviously happened pre-9/11.)

When a newer rebar line was down for service, one plant used to fire up an older, Rube-Goldberg-looking, low-volume and Byzantine line to roll angle iron from the same size heated billets used to make the rebar.