What is the actual probability of food poisoning with food left unrefrigerated overnight? There are two components to risk: probability (how likely is the bad thing to happen) and hazard (how severe are the negative consequences). I know that hazard can be quite bad in case of food poisonings so I'm not surprised official sanitary guidelines often require taking the probability all the way to zero. But as an individual I have a hard time being able to properly evaluate food safety-related risks - not because I don't know the hazard but because I don't know how likely is it actually that dangerous bacteria will develop etc.

When I leave home forgetting my bicycle helmet I can roughly gauge if cycling is a risk worth taking because I know the conditions on the road and can anticipate the probabilities of collision. With a soup left overnight I have no clue of the probabilities involved: is it definitely unsafe? One in ten chance of diarrhoea? One in hundred chance of death? Or maybe one in a million?

I remember from growing up in central-eastern Europe that my family left food unrefrigerated overnight on a regular basis, often intentionally to improve the flavour profile - and so the probability of poisoning is definitely on the low side. Still, with my hypochondriac tendencies, and scared straight by overly conservative safety guidelines I end up throwing out a lot of food these days, which pains me a lot. I want to be able to manage risk in a more informed way so hopefully someone can offer any insight about this.
I'm not sure how answerable this is, as kitchens vary so much. 

A clean, cool kitchen will be very different to a steamy hot, dirty one, in terms of both likelihood of contamination and growth of pathogens after the food is contaminated. Some pathogens are also almost ubiquitous. Homes may be cleaner than they used to be, but in temperate parts of the world they're also warmer. 

It doesn't of course help that the guidance is almost all written for cases where for is being provided for the unsuspecting public (including individuals at greater risk) rather than in the home. 

And then it depends on the food as well. Some support the growth of particularly bad species particularly well (e.g. cooked rice), others tend to spoil in detectable ways before they're colonised by nasties (many dairy products and actually bread).

From my experience I can say that the risk from food left out is really rather small compared to other sources of food poisoning - but a sample size of one is no use. Even if it's not a threat to your overall health, food poisoning is very unpleasant so it's worth a little effort to avoid it by cooling hot food quite quickly and chilling it. I sometimes forget stuff that starts too hot to put in the fridge, but don't waste it, and that's how I know the probability has to be low. That's not a recommendation, far from it.