This short news article is from todays MTV news Germany:

Since the band's Elevation Tour last summer, quite some time has passed. So Bono, when will you be playing Germany the next time? "Some of the band just were tired, and we had a very full schedule over the last few years. There wasn't one night on the last tour that felt like work. But all of it, you know, it was hard, but it felt like magic. And there was a few members of the band that just don't have the energy to commit to it, but I am very sad about that because I really love to play Europe."

The full article (german) can be found here.