Of course, it's easy for you just to take anyone that does out of the smart pool and put them in the dumb pool. The problem is this is in no way a predictive measure. With the rules you have henceforth set you will be unable to classify that a person is smart before any trouble occurs.
This is how the rules you setup look like
You: This person is smart because they put X money in savings and have a backup fund.
[nothing interesting happens to this person]
You: See they were smart...
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You: This person is smart because they put X money in savings and have a backup fund.
[person gets crashed into and injured, then a poorly timed market crash eliminates 70% of their savings driving them into bankruptcy]
You: This person was obviously dumb...
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See, the thing is you, and the vast majority of US on HN are far closer to that second person then we'd like to admin (well short of some of the multi-millionaires that post here). We can just make ourselves feel better by saying we're smart instead of lucky.