I think the answer is, beforehand there are too many contingencies and it seems like a waste in mental effort to consider them all.
Consider the stock example, which is quite simple. I buy a share at $100. I don’t think it’s so simple that I decide in advance I’m going to sell if it drops below $80. What if, in one day, it drops to $83, and I don’t have access to a broker except to sell it at the end of the next day? What if the stock is doing well, and then there’s a rumor that quickly sends it down to $80? What if I happen to have good reason to think the rumor is false? What if it’s doing very well, but then a rumor sends it down to $85? And this time, I think the rumor is correct. What if I’m away from my broker while bad news develops and it drops to $50, but then the bad news appears increasingly not so bad and the stock is rising when I get in contact with my broker again? Etc.
And all this has to do with when to sell a share of stock, which is seemingly characterized by a single number. There is much more that can develop in connection to the scenario you describe.
Nice post. I agree very much. This simple observation goes far to explain trends in how beliefs about religion, politics, race, and gender are handed down from parents to children.
It took me all the way up to graduate school to break the molds of childhood on my political and religious beliefs—and I was helped by a number of factors that most people don’t experience: living away from where I grew up for many years, having unpleasant childhood experiences that I prefer to separate myself from, and, if I may say so, being a very intelligent and critical thinker, at least by all the standard measures.