At 37K feet, above the airplane, tracking really fast moving objects, in the direction the cockpit is facing, we are expecting a phone or a dash cam? C'mon
Well, is op wondering why this can't be done in the future, or are they asking why it's not on video for us to watch right now? Those are two different questions, your answer addressing the former.
If the pilot can see it, certainly a cam from inside the cockpit can see it.
I understand that planes aren't cars but... We have cars doing just that: recording absolutely everything in case something unexpected happen.
It's 2021: I'm sure airliners could have it at some point. It doesn't look like a feature too much out of a science-fiction movie.
And this would settle quite some of the UFO sightings.