It wasn’t selected for. The way I see it, it’s a side effect of humans being evolved for social interaction. Generally when humans would communicate they would see the human they are talking to.

Edit: Your brain has evolved to have conversations face- to-face, which typically involves movement and gesture. Conversing over the phone is an extremely recent part of our evolutionary past. When you talk on the phone, moving and gesturing is pretty useless, but the parts of your brain that are responsible for all that still get activated. So you get up and wander around for lack of anything better to do. (| think there’s also some aspects involving learning style, so if you’re the kind of person who learns best by doing, then physical movement facilitates your thought processes.)

Also this could very well be related to how creative thinking maybe linked to physical movement which makes a full circle back to pattern recognition improvements and human evolution towards recognizing face patterns. (Source)