Why don't we do this all the time?

One of my favorite moments in teaching is asking the question: "why don't we work like this all the time?"

In a training environment, teams are so surprised at the amount of done, working product they can produce during the few short days of class. Getting teams working closely together, sitting around a table, under the pressure of a strict timebox, and working on a single interesting piece of work without interruption. Turns out people not only perform better and are more productive in this environment, they actually like it, find it enjoyable, and are more engaged.  

So I ask you: why aren't we working like this all the time?