It is who they are and reflects much of what goes on around them. Go to Ireland once and you will see where Bono and the guys are coming from in their music. Seeing them in concert is very spiritual and combine that with the music, the energy that is produced during a concert is something one will not forget. It all goes together to reate what is so great about them.
I must have missed the U2 songs on the widespread abuse of children by the Irish representatives of God - namely the bishops who covered up the abuses and facilitated the abusers, abusers who happened to be priests and members of Religious Orders.
Bono in particular would be well able to articulate the kind of society that he came from yet he hasn't in any instance articulated, in his music, anything about the Irish Child Gulags and Magdalen Asylums that incarcerated women and children !
That said U2 concerts ARE unforgettable and Bono in particular is a humanitarian and has supported victims/survivors of abuse and shamed the Irish Government. But as to spirituality .... I think I have more Sympathy for the Devil than any reference to God in the music of U2.
It's funny this thread comes up. It was "holy week" ten years ago that I was vising Ireland...a cab-driver in Dublin told my friends and I where Bono lived. (Oh man, I was so excited I LOVE U2). So we took a DART--a train (electric maybe) to this big hill where it was obvious well-to-do people lived. And we went up the wrong side (the long side) of the road. We made it all the way up the hill, then found Bono's house. It was across the street from some politician's house...I can't remember now.
But the gates were huge...big copper plates on, and inscribed with some poetic verse. We took pictures and video. We were considering ringing the doorbell when somebody yelled at us through the intercom.
I got to see them live in DC as well. Awesome concert. (But it paled in comparison to Pink Floyd. Sorry, Bono).
ETA: Oh yeah...God question. Man, it's their music. God's important to them and sometimes they express it through their music. That's cool, it's beautiful...they also express some of the best of human nature, the worst of human nature, they touch on human sexuality, suffering, love...very inspired group.