When we fill a blank stage with objects and an environment through committed mime, the world we create becomes that much more engaging, for players and audience members alike.  The audience loves to be able to "see" what we create on stage.  And if we really look at what we create on stage, we'll find it easier to generate active endowments that can (and should) affect our play.  If we do as too many improvisers do and stand with our hands on our hips at stage center and engage only our mouths we're putting a lot of undue burden on our words, and we should not aspire to be in-the-moment script writers.  Focus out and engage the world being created around you.  That's good advice in improv as in life.