Others have answered this well, but a more interesting question to me is why we don’t have video of the flight deck recorded on flight recorders. We have the technology to do that reliably.

It’s an interesting privacy concern really. Pilots don’t like the idea, somewhat understandably, who wants to be watched at work every minute of their day? But then it’s also a safety benefit and maybe that’ll win out eventually (this question does keep getting raised on certain crashes).