It's not their job to prevent that.

It is a sys admin's job to mitigate damage from security leaks and to introduce hardened, fault-tolerant security paradigms.

You are just hacking the leaves. Once the secret is posted. It is public, it has multiple copy elsewhere on the internet. Even if you delete there is a copy kept somewhere on the internet -- and that's not an assumption. For example, iirc, Github copy is dumped to google every some-x-time.

Hmmm, it seems like having layered security, where accidentally exposed credentials aren't automatically "game over" would be better than not.

Not sure how practical that is to implement for every technology, but for many it could probably be done.

Seems like a time+money vs risk trade off thing.