JA live at the Family Dog probably has more on it than what has been released I wold imagine.
I'm pretty sure public television KQED in San Francisco has early video of the band pre-Grace Slick. They did a local program called 'Come Up The Years' that also featured Big Brother. I've never seen JA from that. The pic on the back of Takes Off of them on stage I'm pretty certain is from that show.
Monterey Pop I would think has more vid. Altamont maybe, considering the chaos.
I think initially the band only released what they deemed as worthy. Now, who knows. Not worth the money to produce because of low demand perhaps. I think that's probably the reason other than legal issues.
But keep in mind that video recording was pretty archaic then and didn't always produce good results like today so to have a complete show of any band back then is somewhat rare.