The short answer is: It’s because they ARE improvised!
But there has to be a longer answer, because improvisation is famously unreliable. When the actors are at their peak, nothing is funnier, more pure in essence, than spontaneous improvisation. But a big-budget movie has to be good all the way through; every minute has to be perfect. And although I’m a huge fan of improvisation, I have to admit: it’s the opposite of perfect.
Improvisation creates spontaneous magic, but by definition it’s slapdash and unrefined.
The New York Times Sunday Magazine just published a story that reveals how Hollywood channels improvisation to be reliably funny: directors ask the actors to improvise the same scene, over and over again. And then, they hire an editor like Brent White, who combs through hours and hours of improvised digital video clips to select the funniest takes out of an improvised mess:
White’s career coincides with the rise of improvisation as a technique central to Hollywood comedy-making, and his adeptness at giving shape and rhythm to wild excesses of off-the-cuff material put him at the front of his field.
White’s first big hit was the 2004 comedy “Anchorman,” directed by Adam McKay (who I videotaped, long ago, as part of my research at the ImprovOlympic theater, when McKay was improvising as a member of the group called The Family). White has done many of the Adam McKay/Will Ferrell movies, but also Adam Sandler movies and Seth Rogen movies.
Because directors these days use multiple cameras to film every scene, doing improvisation on set results in a huge amount of digital video data. You could only edit in this way recently, when the cost of video data storage has declined dramatically. I love this line from the article:
White’s duties oscillate between those of a gem carver and those of a bricklayer–it’s one thing to perfect a single joke, quite another to assemble a series of these into a movie that stands up straight.
“Bricklayer” because White can’t just choose one single funny line; he has to shape the whole movie, so that the funny lines he selects build together. The funniest line in one scene might not blend well with the funniest line in the next scene, so you have to make compromises. White says “there are all those great things that we wind up taking out.”
White’s most awesome brilliance is choosing the pace and timing between lines of dialogue. Sometimes, adding a second–or taking one out–gets an unexpected laugh. As Director Paul Feig once told him, “sometimes, you just create a joke out of nothing.”