Festivals are filming everything no matter what. I'm pretty sure that LP has it as part of their performance contract that all footage is their property. They are keeping all that, they know it might be valuable some day, concert recordings are getting more popular so they have a ton of stuff IF they ever plan to sell it some day. I'm sure lots of bands do this.
But I can understand it from an artist perspective that just don't release every show all the time for TV or whatever. For example Rock am Ring 2007 were just the highlights the band/management picked. I can also see the label perspective, they sell the rights to TV networks but that's all the money they make from it, just look at all the bootleggers in Japan or Ebay selling every single show that ends up on TV.
I think that this will change in the future, just look a few years back how hard it was to supply this kind of stuff. With todays technology they could easily sell show videos over itunes or over other VOD platforms which happened for a few in the past already. I'm pretty sure they know that there's demand for this stuff, it's maybe just a matter of time.
If you are angry at LP for not releasing enough, just look at Tool, they released NOTHING EVER