Interesting to see this incorrect line of reasoning about risk laid out so explicitly.
If you're around people who do extreme sports with serous risk, you'll know many people who have this attitude and you'll also know many people who incurred life-altering injuries or died because of this attitude.
A friend of mine who's reasonable and has a higher risk tolerance than me used to paddle with a group of whitewater kayakers who were doing the hardest stuff. 4 out of 7 of them died. She says
the reason she's still alive and so many of her compatriots are not is how she thinks about risk.
People would say things like "there's a 99% chance this will be fine", where "not fine" is fatal and they would then run something that had a 99% chance of working out. She wouldn't do that because, of course, if you regularly take a 1% chance of death, you're going to end up dead unless you're extremely lucky.
Another one is that she would never run something she hadn't observed before, whereas
Also, estimating that 99% figure is hard, esp. if you want estimates that take into account various specific things about this particular instance. For many activities, I don't think anyone's trying to do that with any amount of rigor.
I once wanted to compare risks of scuba diving and freediving (for depths up to ~20m) in general. What I gathered from a few afternoons of looking up literature was that risk of dying per day is equal within an order of magnitude (I don't remember the absolute values anymore) and that scuba risk is dominated by accidents preventable by not panicking[1], while freediving risk is dominated by accidents preventable by better planning[2]. If I wanted to learn what are the risks conditioned on e.g. weather (or, more importantly, how weather changes the risks), I would probably be guessing. Similarly, if I wanted to take into account anything about me in those estimates.
In semi-professional situations where one is expected to estimate risk (to determine whether it's acceptable) the accepted ways of doing that are quite far from quantitative, because doing that quantitatively wouldn't work for lack of sources. And not doing it quantitatively makes it harder to notice that the estimates are off, and doesn't make it easier to do it more quantitatively in the future~~~
[1] something like 30~50% of scuba diving fatalities are directly caused by lung barotrauma
[2] some large percentage I can't remember anymore of accidents appeared to be situations where basic buddy observation rules were not followed and contributed to the fatal outcome
