I suspect the people who are "virtually guaranteed" to need payouts are a small population compared to the majority of people that live somewhere in the gray zone between the two extremes.

Then, to quantify the people in that gray zone, it becomes a question of which variables to we include? Sure, alcohol is bad, and junk food is bad. But what is junk food precisely? And if you run ultra-marathons, it surely doesn't matter as much. If you live in a city with higher pollution, if you drive a cheaper older car with a worse safety rating, if you work two jobs and thus have higher stress levels, on and on.

And if we're talking about social healthcare, do you really want a faceless bureaucracy to be tasked with calculating those risks and putting a price on all your life choices?