Why the stoic acting style in 2001 Space Odyssey?

I have watched all of Stanley Kubrick's movies. He wants you to know that he's in control of the pace of the movie. You'll be fed each line when he's ready to feed it to you.

All of Kubrick's movies tend to have a lot of white space, empty space where no one is doing or saying anything; they are merely existing. Listen to the non-human pace of Nicole Kidman's character (in Eyes Wide Shut). You are hanging on every word.

Kubrick creates tension through his use of pace. The actors aren't being stoic. They are moving and speaking at a real life pace, not the pace of normal movies.