Here we find a physical manifestation of unknown and legacy dependencies. These cables have added up over decades of research, and now there’s no room for more! Physically identifying the cables for removal is difficult enough, but a massive project if records over those decades are not precise enough to know the dependencies of each node. It isn’t much of a stretch for this to make us think of analogies in the software world, and it doesn’t take a multi-billion dollar, multi-decade old facility to add these things up. You don’t want the lights to go out when you pull a cable, and you don’t want someone random yelling from down the hall when you change a software service or application. Flipped around, when your app or service stops working, do you know if you have a list of upstream providers who might have changed, in order to check with them?
To know for sure, you must treat code as the source of truth to know what the upstream and downstream impacts of change will be. At least we don’t need gas masks.