Problem is, people can't keep their eyes on the ground and what's in front of them at the same time. Get too focused on what's at your feet, and you might end up walking into a telephone pole.

[Or somebody else, for that matter. He probably should've used a better example in hindsight.]

It's good to stop and look every now and then, but unless you sprouted another head or extra eyes, you can't really take in everything at once.