why improvise?

Of all the ways to practice, structure or perform music, why might we choose improvisation? There’s no right answer to this question, but addressing it may help us to understand what improvisation is. And finding a working definition of improvisation may help us focus our studies.
I’m not trying to to get dogmatic: there is, afterall, a multiplicity of constructive responses to this. Certainly, at least in my case, the reason for choosing improvisation as the primary mode for practicing music has changed (some times radically) over the years. Maybe seven years ago or so I might have approached this question in reference to, say, the “leap into the unknown” as Steve Lacy might have articulated it. I certainly still think about this “leap,” but now I would nominate an idea that was a peripheral issue back seven years ago as the primary reason I remain a card-carrying improviser: Improvisation is about creativity; about accepting the creative impulse in us and in others. It is, in other words, a social act. An act that is simultaneously of the creative and the political.

What happens is what happens; is what you have created; is what you have to work with. What matters is to listen, to watch, to add to what is happening rather that subtract from it—and avoid the reflex of trying to make it into somthing you think it ought to be, rather than letting it become what it can be.

From Anthony Frost and Ralph Yarrow (1990), Improvisation in Drama (London: MacMillan), pp. 2-3

What could be more humyn?