You mean fact.
I think you underestimate the ability of the average concertgoer to distinguish the difference between a standard routine and spontaneity. Concerts are all about spontaneity. If you want a standard routine, go buy the DVD or go to the movies.
Talking from personal experience, when I saw the Finn Brothers live, I had no idea what their setlist was. There was a great spontaneous energy throughout the whole concert, something I have only felt a few times at U2 concerts (at the times I knew they were deviating from their set). Of course, once I got home and checked online, I discovered the Finns had wildly varying sets and I suddenly knew why the atmosphere had felt so good. It really felt like anything could happen at that gig, that Neil could have just started strumming any song he liked - or any song the crowd requested (he indeed invited and played requests). That feeling is pretty much not present at U2 gigs. You can tell it has been meticulously planned, and even if you personally don't know what's about to happen next, you sure as hell know that the band knows and that the spontaneity that lies at the heart of rock music isn't not nearly as present as it should be. And that's too much like going to a play or a movie rather than a concert.
(This is actually precisely why I didn't bother seeing Roger Waters when he visited Melbourne. I don't exactly follow his setlists, but I do know that it almost never changes. In most cases, I can't be bothered going to see an artist who's not going to bring some spontaneity to the table and change it up. Especially not if his second set is a perfectly choreographed Dark Side Of The Snoozefest.)
They're making the best possible show each time, and that includes scripted things and more - or less - fixed setlist and most importantly, the show dictates the song choice. We already have enough mistakes and missed lyrics as it is, imagine the chaos of, rotating 5 songs each night.
