Is It Live or Memorex?

Why is the experience of live performance so different from recorded versions, even of the same performance? It can't be interaction with the artist since it is true for large venues where that sort interaction isn't possible.

Usually, the recorded version seems less energetic or at least less affective. But it can also go in the other direction. It has long been part of Grateful Dead lore that their performance at Woodstock was horrific, terrible, one of the worst. The electrical ground was messed up so that any time Jerry or Bob touched their guitars, they received painful shocks. In addition, the line has always gone that they messed up all the big events and the magic arrived randomly at smaller shows. All of them left the stage considering the set to be a complete disaster start to finish. We were never able to test the claim because the Dead refused to sign the release that allowed the footage to be come part of the Woodstock film and album. (They refused on principle, but no one was ever exactly sure what the principle was...) Recently, the footage was finally released. And, of course, it is not the unmitigated failure they remembered. At least that is what you get from the recording. It isn't the best work of the era, but is passable.

I had exactly the same sense watching my first set on stage as a comic. That looks better than it felt.

So why is the live experience so different from that we get watching the recording?