Mike
My guess is.... economics.
Depending on his funding, he may only have a budget to do a "live" performance. He has two cameramen there, one doing the main shot and the other doing close-ups at the bench, so there is a bit of post-filming editing going on, but not much.
I know from my own efforts that it is phenomenally resource-intensive to shoot, edit, splice to the sort of level we are so used to. I do it because I think the result is better, but then it's my own time. If I were paying someone else to do it, it would be a non-starter.
I just think it's amazing that he can keep going like that without decending into mumbling rubbish.
S