I've recorded and edited a lot of classical music, and the stuff done by pros is a lot easier to splice together: even if recorded weeks apart in different rooms they can match the tempo and pitch exactly, but amateurs can never match that stuff from minute to minute.
Recently, modern music has started using click tracks so that stuff can always be moved around and edited at whim, and the music tech blog the music machinery wrote an interesting piece where they actually analyzed the variations in tempo throughout the songs complete with charts and graphs. Of course, theoretically, people could have been using metronomes long ago and tight drummers could be keeping very consistent tempos without a click track today (or preprogramming variable click-tracks), so it's not hard science, but it's an interesting read nevertheless. I know I've heard more than a few tracks where I thought "man that's tight!" and there was probably no click track involved.
Personally I don't see anything wrong with using the tempo "click" track, even if the implication is that it's a crutch. A lot of great music has been made possible that would never have been possible before because of the ability to drag and drop music in a grid. At the same time, I think the if you don't need it, don't use it philosophy is probably a good one.
For his next exploration, I hope he looks at tracking the pitch and tempo of a college a-capella group. NIGHT-mare!
Thanks to www.extrapepperoni.com for this one.