This is the thing about software: even if you aren't looking to improve it, the world around it will subtly shift so it'll need to be updated or it'll stop working.

For example, Windows XP can't access the modern internet because it doesn't support TLS 1.2 or 1.3 and most of the web is now secure. The software still exists, but the world around it has shifted so it doesn't really work. If 95% of people end up owning electric cars, gas stations are going to become scarce. Maybe there will be workarounds, but the world will have shifted around the product. Let's say that all gas pumps were changed to wider-nozzle pumps. Sure, you could make an adapter, but that's the point: changes in the world around you end up necessitating changes, workarounds, etc.

It might be mostly read-only, but there's always little possible things that come up requiring work to be done on it.