Because the future us will be conditioned to do so by our cryptographically integrated devices. There'll be so much fake video out there that we'll get accustomed to seeing it on our devices with the big huge "fake" sign flashing on it.
(Or, again, even worse, it will not have the "real" sign flashing on it that the video from validated publishers and cameras will have.)
We can be conditioned to do this extremely quickly. Again, ActiveX is what made all the plugin security warnings start popping up everywhere. But after a while, plugins like flash and unity even fell to the reality of us having been conditioned to click "Do Not Run Plugin" whenever we saw that warning. Are we better off without flash and unity? Probably, but that's beside the point. The point is that masses can be conditioned to implement their own control when you set up a system where only data meeting a certain standard is accepted. And it's a hardware standard. Consider very carefully the position over us that such a system would put hardware makers and those with power over hardware makers in.
Now again, I'm not arguing that fakes are not a problem. They are indeed a problem. Just saying we should go about solving the problem with extreme care and caution.
That's my point.
Going down the hardware cryptography path certainly does solve the problem. I'm not here to try and claim that it doesn't. The issue is, 10 or 20 years down the road, how have humans been conditioned because of the fact that only certain cameras can be validated to be real?
If cryptography takes over, 20 years from now, no one is going to convict any guy of rape because they see him on a non-signed camera video, or a non-signed CCTV feed. (And don't get me wrong, they shouldn't convict the guy if that's the so called evidence the prosecutor has.)
What I'm asking is that everyone take a deep breath, slow down for a minute, and just think about the implications of that.
And I was being generous in the scenario I laid out here. In reality, I don't believe it would take 20 years to condition us to dismiss non-signed video out of hand.
I think that's the end goal of all the "deep fake" hysteria we're being primed with. In the future if some damning video of a politician or other elite member of society pops up the defense will simply be "well you can't rule out that it's a fake, look, it's not signed and it's not in our database of trusted videos!"
related: It's telling that "factchecking" isn't a dialogue between various authorities, but instead just a bunch of weird private judicial systems with no appeals courts, selected and assigned to specific stories by internet aggregation intermediaries. Eventually, this can't help but shake out as stories being divided into two categories: factual and banned from distribution.
I sadly feel that we're about 10 years away from licensing journalists with a security clearance-type process that must be sponsored by an approved outlet. The PropOrNot at the Post shook me a bit.
If we're at the point of trusting videos only from select providers, well, that's not really much of an improvement over just finding the video on that provider's website over HTTPS.
Audio and video were sort of aberrant in fact that they could still generally be accepted at face value (as compared to quotes and attributions) and we're very quickly losing that stability.