Handwriting is somehow determined by the method the child follows when learning, there are two main methods, one in which you start drawing dots and then the child links them to form letters, this method provides more regularity in the form and size of them, and there's another one in which you learn each letter by imitation like pictograms, this is faster, but usually the person develops a more varying size, sometimes they even mix uppercase and lowercase.
After years of teaching carreer and of correcting handwritten exercises I don't find Bono's handwriting or those from the other members of the band so extraordinary or difficult to read, they are average, when something has been written as a quick note their style is more casual as it is mine when I leave a note at home, very different from when I write something on the blackboard, but that's the same with everyone I suppose.
I don't know if it is the same where you live, but in my country suggesting that someone is an alcoholic without any proof is a very bad insult and I'm feeling really uncomfortable with some of the statements I've read in this thread.