plenty of far far far older musicians don’t require prompt, to me it just smacks of distance from the music.
it’s tantamount to miming, it might work for their massive ‘hide behind the production’ tours where the show is more theatre than music but a festival performance is about the music. Bono even said ‘it’s the first time we haven’t played in front of our own audience’. Don’t get me wrong, i like a lot of U2 songs and their tours are an awesome spectacle but they missed the spirit of glasto completely. As does their security trampling on the tax protest.
just my opinion