If there are 10 houses, a burglar tries to get into all 10 but only succeeds on 2, then you should talk to the 8 owners who successfully protected their houses. If there are 1000 houses, a burglar tries to get into 10 but doesn't tell you which 10, and succeeds on 2, you should talk to those 2 owners because they know for a fact what can fail. 990 owners will just say "do what I do" without having any evidence that their strategy is actually safe.