Because, believe it or not, it's often hard to tell the difference, especially if you know about mind projection fallacy. I tend to give people the benefit of the doubt.
Plus most people avoid creating a confrontation because that also could put them in a negative light. (Not only do you have to think what the other person is doing is bad, but the majority of other people have to think that as well, for you to get any value out of the confrontation.)
The other day, someone did something I didn't expect. It was something many people have done before; something that I thought of as very normal, but that I in no way understood and had not predicted.
As I said, this had happened many time before, so I wrote it off as "me not understanding people" or "people are weird" for a second, like I usually do, before realizing that "bad at" really means "lacking basic knowledge", which I had never realized before.
And then I thought "I should ask someone who is different from me why people do that, and eventually someone will have an answer."
But many people will have many more questions like this. So, what have you observed people doing time and time again, but never understood? Or something that you only understood after a long time or asking someone about it?
And can Less Wrong tell us, not necessarily why (I for one can make up evolutionary psychology fairy tales all day if I want) but what conscious thought process occurs behind these events?