Why is it done? A bunch of reasons: it's adorable,it's easy to rehearse, lots of parts, sentimentality, most of the scenes are incredibly accessible to younger people and relatively simple sets. It can also be done easily cut (with permission - which is always granted to the best of my knowledge)
I directed it about 5 years ago and we all had a great time, and the audience loved it to.
If you have specific questions, hit me up.
(BTW, my hs group - not the same kids that performed in it - had a talk back session after Band's Visit and Cariani was part of it. I chatted with him for a few moments afterwards where I told him how much we had enjoyed producing it. He seemed incredibly touched by that.)
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.