Cost efficient for your team’s budget sure, but a 1% chance of a 10+ million dollar issue is worth significant effort. That’s the thing with enterprise systems the scale of minor blips can justify quite a bit. If 1 person operating for 3 months could figure out what something is doing there’s scales where that’s a perfectly reasonable thing to do.
Enterprise covers a while range of situations there’s a lot more billion dollar orgs than trillion dollar orgs so your mileage may very.
In a reasonable organization only very minor systems can be undocumented enough to fall through the cracks.
Stuff that’s been working fine for years is easy for a team to forget about, especially when it’s a hidden dependency in some script that’s going to make some process quietly fail.
> Stuff that’s been working fine for years is easy for a team to forget about
That's why serious companies have a documentation system describing their processes, tools and dependencies.
Documentation on every possible system that could use the resource would need to be accurate, complete, have someone locate and actually read it, remember, and communicate it with someone in a relevant meeting which may be taking place multiple levels of management above the reader here. As part of that chain when a new manager shows up and there’s endless seemingly minor details, so even if they actually did encounter that information at some point theirs nothing that particularly calls out as worth remembering at the time.
That’s a lot of individual points of failure which is why I’m saying in the real world even well run companies mess this stuff up.
1) I was (temporarily) the only one still at the company who knew why it was there
2) I only knew myself because I had reverse engineered it, because the person who put it there had left the company
Now, some of those things had indeed become unnecessary over time (and thus were removed). Some of them, however, have been important (and thus were documented). In aggregate, it's been well worth the effort to do that reverse engineering to classify things properly.