Your evasiveness is transparent. I don't think you should go to the hospital with every headache for the same reason you don't; aneurysm are rare. Now please provide a direct answer rather than trying to weasel around the point. Why do you assume that you headache is just a headache and not an impending aneurysm? Why, if you happen to be in your house, do you assume that the footsteps you hear are your wife's and not an intruder's? Why do you assume that there is no invisible truck coming at you? For several posts you have transparently avoided giving direct answers to the straightforward questions I have posed. Your unwillingness to directly answer these questions indicates that you know I'm right: you are instinctively using parsimony all the time.
Your supposed point relies on too many assumptions to be valid. First of all, you assume that I hear footsteps in my house. I never do. Second, you assume that I don't go to the hospital every time I have a headache because I parsimoniously assume that aneurysms are rare. If I really thought I was having an aneurysm, I would take additional vitamin C not go to the hospital. The same hospital system that I have access to is the one that accidentally amputated both guys legs rather than just the one when he was diabetic. No thanks -- the risk is great and the alleged benefit is minimal.
The only part of your argument that even partially makes sense is the claim that an invisible truck might be hurtling through the intersection by running the red light while I am venturing forward with a green light. If we assume, however, that the invisible truck might exist and is willing to violate laws at will, then it will be impossible for me to determine where it might be and what it might be doing. As such, both staying still and moving are probably equally dangerous whereas moving takes me towards my ultimate destination and thus has more going for it than does the alternative.
Let's assume, for the sake of argument, that there is an invisible truck that habitually comes round my house and routinely violates all the law of the road since a police officer will never detect these violations. There are two possibilities: either the truck is trying to hit me or the truck is trying not to hit me.
If the truck is trying to hit me, then it will be difficult, if not impossible, for me to avoid it because it's invisible and undetectable. Accordingly there is little I can do except wear my seat belt, something I already do as the claimed benefits are great and the cost is small.
If, however, the truck is trying to avoid me, then the best thing I can do is to drive in a normal, predictable manner including appropriate signals for both lane changes and turns, trusting that the invisible truck driver will take this into account to the best of his or her ability and thus avoid me as much as possible.
What does any of this have to do with parsimony?