People driving badly can kill a whole family. But I have never felt the need to attach a camera to my car to get all these people into trouble
What! Are you saying those who drive so badly that they could potentially kill someone shouldn't 'get into trouble' ??????
It's easy to become blase about personal safety when you're surrounded by a metal cage/airbags/crumple zones, but as others have pointed out, on a cycle you're far more vulnerable, and it's not easy staying calm when an inconsiderate motorist causes you to fear for your life. What do you expect cyclists to do, blow 'em a kiss? I admit that in the past I have shouted aggressively at motorists when perhaps I shouldn't have, but I've now learned to be more philosophical and take a more zen-like approach like MacBludgeon and acknowledge good driving with a wave and a smile. After all, motorists are human too and do make genuine mistakes, but what about the ones who shout needlessly at cyclists, or idiots like James Martin who deliberately go out of their way to scare cyclists, or use their vehicles to bully cyclists out of the way (and this is not a myth, it does happen). I would never shout at someone for using a mobile, for instance, but having already been hospitalised with serious injuries by a careless driver (and there are plenty of others out there with similar experiences), I reserve the right to get annoyed when I come close to another serious incident!
I do agree that some of the headcam footage I've seen on here does seem to be about trivial incidents, but I still think helmet cams are a good idea, if for no other reason than if I were to have (another) serious accident then a camera could provide invaluable evidence of what caused an accident, rather than relying one persons word against anothers.
People drive for many reasons, some because their job demands mobility/need to commute great distances/have to travel when or where public transport is not adequate, and for many other reasons I can't think of right now, but if you're trying to suggest that all car journeys , or even a large majority, are essential travel then I think you're seriously mistaken (and I'm talking about domestic car ownership, not commercial traffic). Car ownership is often a lifestyle choice, and I don't have a problem with that, that's there choice. I choose not to drive, that's my choice,but I shouldn't have to risk life and limb every time I ride my bike - though I often do!