because true stories change little by little as they get told, until you end up with something that doesn't even resemble what actually happened
I used to teach social studies. In my first lesson I would tell my students not to trust what I say. I told them that no matter how honest I was, I was going to be mistaken, sometimes at least. Take nothing at face value, I warned them. Question everything. It was probably the best piece of advice I gave in my career :)