Also, my guess is compared to other features they work on this would be fairly trivial, or at least in the same ballpark. And I think it would immediately give the camera a certain cache that would signal "professional" or "serious" that would increase its value, regardless of whether or not the user really needs it.
Without meaning to be dismissive of the large numbers of people who do need these types of cameras (I have close loved ones who are professional photojournalists who rely on having the best cameras), I think a large proportion of people who who buy them don't need them relative to what's on decent phones today. They're just a status symbol for them anyway.
Ultimately, people drop thousands on a pro camera in order to shoot beautiful pictures, not because they want to write their firmware, so you have a chicken-and-egg situation. And while a few people do write amazing firmware - Magic Lantern being an excellent example - that's a liability on a commercial shoot. I might use ML on an art or micro/no-budget project, but as a producer I'd probably nix the idea; you absolutely don't want to be locked into someone's quirky personal workflow to the extent that you can't fire them if they turn out to be shitty photographers or hard to work with on set.
Of course not many people are going to literally write their own firmware, but I can see it being compelling to be able to expand your range of codecs, LUTs etc in a relatively cheap camera, and not have to put up with what the manufacturer thought you'd like.
As for ML, I think it's unlikely to destroy your shoot if you stick to the basics like the focusing and exposure tools (I forget what it actually offers tbh). RAW and more experimental features are probably a bad idea on anything serious, but then so is using a consumer Canon camera.
While I do share many of the photos I take, I don't just dump the entire SD card to Facebook, I want to pick and choose which photos I share.
As for kids... most people are just posting it straight to Facebook anyway. Again, some might care about privacy, but not enough to make it a real premium feature, I suspect.
Naturally people want to pick and choose which photos they share, but that doesn't mean they are worried enough about the ones they didn't choose falling into the wrong hands to pay a premium and put up with cumbersome decryption procedures - they just don't like those photos as much.
at least that is probably what trump has been telling himself at night since everyone turned him down to perform at his inauguration speech.
for everyone else. kinda a big incentive.
Having said that, it's not inconceivable that camera makers can solve this problem (a) cheaply and (b) in a way that is "off by default" for most consumers but available if needed. But I'm not holding my breath.
I think it's far more likely that we'll see the quality of phone photo/video quality become "good enough" for security-sensitive users to abandon standalone cameras entirely than that we'll see camera encryption catch up in the other direction.