They AUDIO record every show. Video is another story. They will usually video a few shows per tour and then pick the best to release on DVD.
Case in point, there is a pretty professional looking bootleg of Wash DC Outside Broadcast. Why not an official release? While the video is good there were errors in the show. Notably, Edge f*&^ing up the piano on NYD. Then again, they did leave in The Edge tossing his Rickenbacker to the ground in Boston 2001.
Some of the other great footage out there are shows that were filmed by local (to the country of the show) crews. Examples being MTV filming PopMart Santiago and Sao Paulo Brazil for those countries. Again, in those cases the shows are filmed and shown on TV as U2 are only playing 1-2 shows in the region and not everyone that wants to see them can get tickets or tickets/fare to the show.
I just saw a great video from Vertigo Sao Paulo. The only annoying bit, as it was on Brazil TV, it has subtitles... in portugeuse... for the lyrics! Ack. Other than that, it is beautifully shot and highly recommended if you can get your hands on it.
i have the dvd from the sao paulo show. indeed this dvd is fantastic , even better than the real thing. the sub titles apper just in the few first songs.
Unfortunatly i have ZERO bootleg DVD's, but would love to get my hands on a few of the older pro shot concerts from the Boy, October, War & U'Fire tours.
If some one would contact me, perhaps we could make some kind of deal.