Why aren’t all personal security cameras and dash cams encrypted by default?

Why wouldn’t a dash cam automatically be encrypted as it is stored. If a driver gets into an accident that is their fault, without encryption, the footage will be available to anyone who has access to it. Shouldn’t the owner of the footage also own the option to use it as they please?

I’m in no way encouraging or condoning illegal or irresponsible behavior, just asking why this isn’t a default option provided by security and dash cam product providers.

A few years ago, when police searched Aaron Hernandez’s home, they found hours of footage from his 14-camera surveillance system. While he’s certainly a reprehensible individual, his footage should have been encrypted. I can’t help but feel that I would want all of my private video footage to be encrypted by default, and only I should hold the keys. To add another layer, I would also want the footage to be deniable. I’m neither a legal or encryption expert, so I’m not going to speculate how to do this in a way which is actually deniable, but it should be default, or at least an option.