It's on every thread now, and it's so annoying. It's just a way to feel superior to OP, usually. And some of them are just bloody ridiculous - "why didn't you anticipate a comet falling on your car as you were driving home and bring a spare car? That's what I would have done".
The thing is, whatever the OP could or should have done, whatever might have been the sensible thing or the best thing or the right thing, they didn't do it and that's why they're posting. And as turning back time isn't an option, it doesn't actually help to tell them what they should have done. Advice along the lines of "next time, it might be an idea to...", is ok, or "this happened to me, so I...". But the "why didn't you" posts are really putting me off reading threads now. Sometimes the stretches people go to are just insane, as well. If you're about to post a sentence like that, please, stop and think, is It helpful? Or are you just trying to stick the boot in?