That's a vanishingly rare situation, that I'm surprised to see you arguing for, given your other comments about the futility of enforcing invariants on reality. ;)

If something does meaningful and valuable work, that almost always means it's also valuable to exploit.

We can agree that if you're talking resource-commitment risk (i.e. must spend this much to exploit), there are insecure systems that are effective to implement, because the cost of exploitation exceeds the benefit. (Though warning: technological progress)

But fundamentally insecure systems are rare in practice for a reason.