> vulnerabilities are just left in play until someone malicious comes along and decides to do some real damage. But that seems so silly

Well, that's exactly how it tends to work for housing, so I think GP's point is that if it works there it should work here. However, I disagree because the stakes are so different (harming a single family who are free to harden however they like, versus harming the general public who are at the mercy of whatever hardening is done for them).