Coronary calcium deposit scans are cheap and extremely effective at giving a probabilistic window of possible future heart attack, but doctors don't order them prior to a CVD event, and insurance doesn't cover them as a pre-CVD elective.
Instead we're told: We have no way of knowing if or when you'll experience infarction, it's one of God's Great Mysteries. Just don't eat eggs and pray.
You're absolutely right, but the entire medical industry has no intention of actually reducing mortality. It's a cash grab from top to bottom, and preventative monitoring of the kind you suggest already has precedent in coronary calcium scanning. It's not going to happen if it reduces the overall predicted revenue per patient.
In the same way that a single triple-bypass surgery is far more lucrative than a hundred coronary calcium scans, a full course of cancer treatment is absurdly more profitable than regular tissue carcinogen testing.