I disagree with your disagree. Would you stop a witness statement from being taken? Dash-cam footage is effectively an unbiased witness statement. It's not perfect but can certainly prove who is at fault the vast majority of times (both for and against you). Having been on the other end of someone lying when they crashed into me (and there were no witnesses, he turned left in the right-hand lane), I was only saved by the other parties stupidity towards the police otherwise I would have been stuffed. This was before I had a dash-cam.
You are under the assumption that everyone is truthful which is a noble stance to take. Unfortunately it is not true and never will be
I'm not denying that Dashcam is (usually) incontrivertible evidence. But taken to the extreme, I could wear one on a helmet as I walk around all day long to capture absolutely everything I ever witness "just in case".
Flipping it round - has a persons' own dashcam evidence ever been use against *themselves* successfully? I'd personally make it a legal requirement (if it is not already) to hand over dash cam footage (if fitted) in any accident, irrespective of the initial "blame". I fear their use in such cases is a little "one sided" or selective at the moment. Used where the defendant has one, but if the accused/responsible party has one, they may not be required to hand it over as evidence.
I know its futile to expect the whole world to be "nice" and "honest". But driving round videoing everything just to me symbolises everything wrong with modern life/blame culture, and I'm happier not participating in it even if that places a small risk (or more accurately fails to remove an existing risk) on myself. That's the attitude that personally on balance makes my own life happier.